feat(brand): configurable app name — BOR_APP_NAME drives /api/config + the frontend brand layer

One env var (BOR_APP_NAME, default "Brain of Reese") now drives the app's
display name everywhere (TODO.md L12 — owner ask: "a way to customize the
name for 'Brain of'. Should be an env var."). The existing app_name setting
is the source of truth (phase locked decision — no new variable, no rename);
with the variable unset the app is byte-identical to before.

Endpoint (A10 public/stateless, no secrets):
  GET /api/config → exactly {app_name, version} (app/api/config.py, the
  health.py pattern; registered before the static mount). Integration tests:
  anonymous 200, default values, a Settings override follows, key set is
  exactly two keys — no other setting may leak in later.

Frontend brand layer (A11 — runtime fetch, static templates stay static):
  assets/brand.js — a CLASSIC script, first on all six pages, so its top
  level runs at parse time: window.BOR_BRAND = "Brain of Reese"
  synchronously (the default renders immediately, no blank flash), then a
  no-store fetch of /api/config applies the name — document.title (global
  replace), every .brand-text (a name starting "Brain of " keeps the bold
  split Brain of <strong>rest</strong>, any other name renders plain; the
  operator-controlled name is HTML-escaped before innerHTML), a TreeWalker
  over text nodes (script/style rejected — page source never rewritten),
  and the aria-label/placeholder/meta-content attributes. Fetch failure
  keeps the default + console.warn (the loadHealth house style).
  app.js (status labels, typing label, elapsed-hint aria, tool labels) and
  document.js (viewer titles) read window.BOR_BRAND at CALL time via
  brand() — a label set after the fetch lands carries the configured name.
  Containerfile: esbuild minify line for brand.js (classic, like markdown.js);
  the phase-33 ?v= cache-busting picks the new asset ref up automatically.

E2E (A16 — one story, one file, isolated): test_configurable_brand.py boots
a SECOND app instance (same DB/mock-LLM/admin-auth env block, port APP_PORT+1,
BOR_APP_NAME="Brain of Testy") — the shared conftest server keeps the
default name so every other suite's title/label assertions stay untouched —
and asserts /api/config on both instances, the index title/brand/greeting/
#messages aria-label, the sources + login page titles, and one pre-token
chat turn (think out loud marker) whose #send-status reads "Brain of Testy
is thinking"; the no-op regression pins the shared server's default bytes.

Docs: .env.example App section + README configuration reference — what it
affects (titles, header brand, status labels, aria text), the default, the
bold-split rendering rule.

Gates: 695 unit+integration passed, app/ coverage 99% (>90%), story E2E
green in isolation (two consecutive runs), brand-string suites (smoke,
shared header, header consistency, chat persistence) green, ruff + pyright
clean.

.agent/phases/complete/39_configurable_brand/01_config_endpoint.md

@@ -0,0 +1,27 @@
+# Task 01 — `GET /api/config`
+
+**Phase:** `39_configurable_brand` · **Source:** `TODO.md:12 — "Also need a way to customize the name for 'Brain of'. Should be an env var."`
+**Story:** `.agent/user_stories/configurable-brand.md`
+
+## Objective
+A public, stateless endpoint that hands the frontend its display name (+ version) — the single source the brand layer reads.
+
+## Work
+1. `app/api/config.py` — a new router mirroring the `app/api/health.py` pattern:
+   ```python
+   @router.get("/config")
+   def app_config(settings: Settings = Depends(get_settings)) -> dict[str, str]:
+       """Public app metadata for the frontend brand layer (phase 39)."""
+       return {"app_name": settings.app_name, "version": settings.app_version}
+   ```
+   Public (no `require_admin` — the brand must render for anonymous users too, before any sign-in); stateless (A10); the response carries **exactly** these two keys (no other setting may leak in later — the test asserts the key set).
+2. `app/main.py` — register it with the other routers (`app.include_router(config_router, prefix="/api")`), before the static mount (API routes take precedence — same order as the existing routers).
+3. Tests (follow the health test's location and pattern): 200 for anonymous; default values (`"Brain of Reese"`, the current `app_version`); with an overridden `Settings` (`app_name="Brain of Testy"`) the response follows; the response key set == `{"app_name", "version"}`.
+
+## Testing & Quality
+- The tests above; full `uv run pytest` green.
+- Coverage: **>90%** on the new module (keep the handler + docstring tight so it stays covered).
+
+## Completion Criteria
+- [ ] `GET /api/config` (anonymous) → `{"app_name": "Brain of Reese", "version": "0.1.0"}` (the current default version).
+- [ ] The suite green; `uv run ruff check . && uv run pyright` clean.

.agent/phases/complete/39_configurable_brand/02_frontend_branding.md

@@ -0,0 +1,34 @@
+# Task 02 — `brand.js` + de-hard-coding
+
+**Phase:** `39_configurable_brand` · **Source:** `TODO.md:12 — "Also need a way to customize the name for 'Brain of'. Should be an env var."`
+**Story:** `.agent/user_stories/configurable-brand.md`
+
+## Objective
+Every visible brand string on every page resolves from one place (`window.BOR_BRAND`, fed by `/api/config`) — the default "Brain of Reese" renders immediately, and a fetch failure falls back to the default (the page never breaks).
+
+## Work
+1. `frontend/assets/brand.js` — a new small **classic** script (vanilla, no CDN — A11; not a module, so its top level runs at parse time):
+   - Top level: `window.BOR_BRAND = "Brain of Reese"` (synchronous default — module scripts execute after parsing, so the page scripts can read it from the first line).
+   - DOM application (deferred: `if (document.readyState === "loading") document.addEventListener("DOMContentLoaded", applyBrand); else applyBrand();`):
+     1. `fetch("/api/config", { cache: "no-store" })`; on success with a non-empty `app_name`: `window.BOR_BRAND = app_name`, then:
+     2. `document.title = document.title.replaceAll("Brain of Reese", name)`.
+     3. Every `.brand-text` node: if the name starts with `"Brain of "` → `innerHTML = 'Brain of <strong>' + escapeHTML(rest) + '</strong>'` (the current look for the default name); else → `textContent = name` (plain, no bold). **HTML-escape the name** (an operator-controlled string must not inject markup).
+     4. A `TreeWalker` over the document's text nodes: replace the literal "Brain of Reese" with the name (catches the index empty-state h1 "Hey! I'm Brain of Reese." and any prose).
+     5. An attribute pass over `aria-label`, `placeholder`, and meta `content` attributes containing the literal → replace (the `#messages` aria-label "Conversation with Brain of Reese", the input label, the meta descriptions).
+   - On fetch failure: keep the default, `console.warn` (the `loadHealth` house style — progressive enhancement, never break the page).
+   - Small local `escapeHTML` helper (the `markdown.js` pattern — do not import across modules unless the build makes it easy).
+2. The templates (`frontend/index.html`, `sources.html`, `tuning.html`, `document.html`, `login.html`) — add `<script src="assets/brand.js"></script>` **before** the page's module script on every page (classic script → runs at parse time; the module scripts execute later). No other template changes — the walker + attribute pass is the single mechanism; do **not** add `data-brand` markers. The phase-33 `?v=` rewriting picks the new ref up automatically (`app/core/caching.py` matches any `src="…assets/…"`).
+3. `frontend/assets/app.js` — replace the "Brain of Reese" literals with `window.BOR_BRAND` reads: the `UI_STATE` labels (~L107: "… is thinking" / "… is answering"), `TYPING_LABEL` (~L112), the elapsed-hint aria-label (~L540). Pattern: `const brand = () => window.BOR_BRAND || "Brain of Reese";` + template strings. (Mid-turn staleness: a label set before the fetch lands keeps the old name for that turn — accepted, see the phase's locked decisions.)
+4. `frontend/assets/document.js` — the page titles (L147/152: `${doc.title} · Brain of Reese` / `"Document not found · …"`) → use the same `window.BOR_BRAND` read (document.js is a module — `window.BOR_BRAND` is set by then).
+5. `Containerfile` — add the esbuild line for the new file next to the others (L17–23 pattern, classic script like `markdown.js`): `esbuild ./assets/brand.js --minify --outfile=/out/assets/brand.js`.
+6. Verify the no-op property: with the default settings the rendered DOM text is byte-identical to pre-phase on all five pages (the replace is a no-op for the default name) — the existing suites' title/label assertions are the guard; if any assert a string this task moved onto `window.BOR_BRAND`, the default path must render the identical bytes.
+
+## Testing & Quality
+- No Python logic — the story E2E (task 03) is the gate; the existing suites (which assert the default "Brain of Reese" titles/labels against the shared conftest server) must stay green **unchanged**.
+- No CDN (rule 6): no new external tags. UI Structure Check (rule 5): no landmark/contrast change — the brand text keeps its existing classes and styling (the `innerHTML` rewrite only re-emits the same structure with the new name).
+
+## Completion Criteria
+- [ ] `BOR_APP_NAME` unset → all five pages render exactly as today (existing suites green).
+- [ ] `BOR_APP_NAME="Brain of Testy"` → title/header/greeting/labels/aria all carry the new name (asserted by the story E2E, task 03).
+- [ ] The Containerfile build includes brand.js; the asset ref is versioned like its siblings (phase 33).
+- [ ] `uv run pytest` green; `uv run ruff check . && uv run pyright` clean.