phase: 153_document_viewer_context

That last `--co` (collect-only) run was my probe mistake — it shows 34% because no tests execute under collect-only. The valid coverage run was the real gate command executed earlier: `uv run pytest --cov=app --cov-report=term-missing` → **TOTAL 99%** (exit 0, all 3544 tests executed). All gates are verified.

## Phase 153 — final verification pass report

**Verified (all tasks 01–04 complete in `complete/`):**
- Modal `fullPageUrl(source, path, back = null)` + `openDocumentModal(…, back = null)` with module-level `currentBack`; 5 chat call sites pass `"/"`, sources.js call site unchanged (byte-identical Sources path); `documentUrl` comment now true
- Copy-path control (shared `renderDocument` core, icon+text, text = accessible name) on both surfaces; per-page clipboard helpers with the fallback-field + status-line contract; `#doc-copy-announcer` live region; styles + 44px touch floor
- Unit pins: `&back=%2F` / no-`back` byte-identity, `currentBack` single-writer guard, copy strings byte-pinned, phase-13 regression pins untouched

**Test / lint / coverage results:**
- `uv run pytest` → **3544 passed**, 0 failed (full unit + integration)
- `uv run pytest --cov=app --cov-report=term-missing` → **TOTAL 99%** (>90% gate)
- `uv run pytest tests/e2e/test_document_viewer_context.py -v --no-cov` → **8 passed** in 47.33s, in isolation (DB up, mock LLM)
- `uv run ruff check . && uv run pyright` → clean (0 errors/warnings)

**Completion criteria:** all met — (1) chat→modal→Full page: `href="/"` + "Chat"; Sources→modal→Full page: `href="/sources.html"` + "Sources" with `back=` asserted absent; (2) no-`back` URLs byte-identical to pre-phase; (3) Copy path: "Path copied." on success (clipboard readback), prefilled select-on-focus fallback field + "Path ready — copy it from the field." on rejected clipboard, both surfaces parameterized; (4) copied string exactly `docs/homelab/kubernetes.md`; (5) full suite green, E2E isolated green, lint clean, coverage 99%; (6) commit by harness.

**Documentation:** README.md reviewed in full — phase-153 feature already named in the Chat section; routes, env reference, workflows, deployment all consistent — no changes needed. AGENTS.md reviewed in full — rules, gates, and quick-reference commands verified against the repo (incl. `test_smoke.py`, `.env.example`, gitignore entries) — consistent, no changes needed.

**Notable:** pytest 9.1.1 quirk — a doubled `-q` (pyproject `addopts` + explicit `-q`) swallows the final "N passed" summary line while still exiting 0; the plain `uv run pytest` gate command prints it. No defects found in prior work.

**Next pending phase:** `154_sync_status_freshness`.

frontend/assets/app.js

@@ -439,10 +439,13 @@ function scrollReveal(wrap, behavior = SCROLL) {
  * The href a source chip carries: the dedicated viewer (no-JS /
  * context-menu escape hatch). Phase 26: the chip's left-click is
  * intercepted and the document opens in the same-page modal instead
- * (document-modal.js) — this URL is also what the modal's "Full page"
- * link points at. All query values are percent-encoded: real paths
- * contain slashes and sometimes spaces, which would otherwise corrupt
- * the query string. `back` tells the viewer which page to return to
+ * (document-modal.js) — phase 153 (task 01) made the chip's click
+ * pass THIS SAME `back` to openDocumentModal, so this URL is also
+ * what the modal's "Full page" link points at (the chat path:
+ * `&back=%2F` rides along; Sources links omit it on both sides, so
+ * their URLs stay byte-identical to pre-phase). All query values
+ * are percent-encoded: real paths contain slashes and sometimes
+ * spaces, which would otherwise corrupt the query string. `back` tells the viewer which page to return to
  * when its back button is clicked — the chips live in the chat, so chat
  * passes "/" (the viewer validates it: only same-origin relative URLs
  * are honored; Sources links omit it and get the viewer's /sources.html
@@ -1697,7 +1700,7 @@ function appendSources(wrap, sources) {
       chip.addEventListener("click", (e) => {
         e.preventDefault(); // no new tab (phase 26) — the modal takes over
         e.stopPropagation();
-        openDocumentModal(s.source, s.path, chip);
+        openDocumentModal(s.source, s.path, chip, "/"); // back → the chat page (phase 153)
       });
       chip.textContent = label;
       chip.title = label;
@@ -1759,7 +1762,7 @@ function appendRelated(wrap, related) {
     link.addEventListener("click", (e) => {
       e.preventDefault(); // no new tab (phase 26) — the modal takes over
       e.stopPropagation();
-      openDocumentModal(s.source, s.path, link);
+      openDocumentModal(s.source, s.path, link, "/"); // back → the chat page (phase 153)
     });
     link.textContent = docLabel;
     link.title = docLabel; // full path as the native tooltip (chip pattern)
@@ -1801,7 +1804,7 @@ function appendSourceImageFigure(meta, s) {
   fig.addEventListener("click", (e) => {
     e.preventDefault(); // no new tab (phase 26) — the modal takes over
     e.stopPropagation();
-    openDocumentModal(s.source, s.path, fig);
+    openDocumentModal(s.source, s.path, fig, "/"); // back → the chat page (phase 153)
   });
   const img = document.createElement("img");
   img.className = "source-image-img";
@@ -1822,7 +1825,7 @@ function appendSourceImageFigure(meta, s) {
     chip.addEventListener("click", (e) => {
       e.preventDefault(); // no new tab (phase 26) — the modal takes over
       e.stopPropagation();
-      openDocumentModal(s.source, s.path, chip);
+      openDocumentModal(s.source, s.path, chip, "/"); // back → the chat page (phase 153)
     });
     chip.textContent = label;
     chip.title = label;
@@ -1905,7 +1908,7 @@ function appendAnswerImage(wrap, ref) {
   fig.addEventListener("click", (e) => {
     e.preventDefault(); // no new tab (phase 26) — the modal takes over
     e.stopPropagation();
-    openDocumentModal(ref.source, ref.path, fig);
+    openDocumentModal(ref.source, ref.path, fig, "/"); // back → the chat page (phase 153)
   });
   const img = document.createElement("img");
   img.className = "answer-image-img";