feat(docs): save the whole chat session as a doc

Phase 75 (TODO.md L4): "Save as doc" now drafts a document from the
ENTIRE chat session — every question and answer up to the click, in
order — instead of only the clicked bubble's answer; the existing
doc-edit screen's free-form body editing is how the user edits out
anything they don't want to keep from previous replies (no new UI
surface).

Task 01 (frontend):
- app.js buildSessionTranscript(): walks the bor.chat.v1 conversation
  record in order — a numbered section per user turn ("## N.
  <question, raw>" + blank line + the raw answer text; more answers
  join under the same heading), sections blank-line separated, all
  trailing whitespace collapsed to one final newline. Only the raw
  persisted text travels (m.who + m.text — no thinking blocks, no
  source chips, no tune metadata); a brain record before the first
  user record is skipped; a heading-only section marks a user turn
  whose answer never landed (A6, owner-confirmed 2026-09-08).
- saveAsDoc(btn): the draft body is buildSessionTranscript(); the
  dead single-bubble markdown parameter is dropped (the button's
  appendSaveAsDocButton signature is unchanged — one button per
  bubble). Title/path/double-click guard/hand-off are unchanged
  (defaultDocTitle: the last question, whitespace-collapsed,
  <=120 chars; docs/<slug>.md).
- Unit: the app.js source pins move to the transcript shape (whole
  session, no thinking, no dead parameter).

Task 02 (E2E):
- tests/e2e/test_save_doc_session.py (bare-repo fixture, the
  phase-59 convention — git as source of truth): three DISTINCT
  on-topic turns in one session (turn 1 carries the phase-17
  "think out loud" trigger so its record has a thinking block the
  transcript must exclude) -> save on the LAST bubble -> the
  prefilled body is ## 1./## 2./## 3. in order, byte-exact against
  the deterministic mock, thinking-free -> edit the whole
  section-2 block out of the body -> push -> git show
  bor-docs:<path> equals the EDITED body byte-for-byte (section 2's
  question and answer provably absent; sections 1 and 3 byte-exact;
  the UI's sha prefix is git rev-parse bor-docs). Second test:
  the button on the FIRST bubble still drafts the whole session
  (A6 — the transcript is the session at click time, title stays
  the last question); canceling leaves the branch tip untouched.
- tests/e2e/test_response_to_docs.py: the phase-59 single-turn body
  expectation moves to the transcript shape ("## 1. <question>" +
  the answer's markdown) — the rest of the suite unchanged.

Also lands the phase-74 file moves (00_phase.md /
03_mock_marker_e2e.md -> complete/) and the phase reports — the
house convention of committing .agents/ with the phase.

tests/unit/test_save_as_doc_button.py

@@ -240,19 +240,64 @@ def test_app_js_slug_rule() -> None:
     assert "docs/${docSlug(title)}.md" in js
 
 
+def test_app_js_transcript_covers_the_whole_session() -> None:
+    """Phase 75 (TODO L4, A6): buildSessionTranscript() — the draft
+    body — is the WHOLE conversation: a numbered section per USER turn
+    ("## N. <raw question>" + blank line + the raw answer text; more
+    answers join under the same heading), sections blank-line
+    separated, ALL trailing whitespace collapsed to ONE final newline.
+    Only the raw persisted text travels (m.who + m.text — no thinking
+    blocks, no source chips, no tune metadata); a brain record before
+    the first user record is skipped; a user turn whose brain record
+    never landed is a heading-only section. saveAsDoc POSTS the
+    transcript (the phase-59 single-bubble body no longer travels)."""
+    js = _text(APP_JS)
+    fn_idx = js.find("function buildSessionTranscript() {")
+    assert fn_idx != -1, "buildSessionTranscript missing"
+    fn_end = js.find("function appendSaveAsDocButton", fn_idx)
+    assert fn_end > fn_idx
+    fn_body = js[fn_idx:fn_end]
+    # One section per USER turn, numbered 1-based in record order…
+    assert 'm.who === "user"' in fn_body
+    assert "sections.length + 1" in fn_body
+    # …"## N. <question, RAW text>" — the record's text verbatim
+    # (no title transform, no HTML).
+    assert "`## ${sections.length + 1}. ${m.text}`" in fn_body
+    # …the RAW answer text joins under its question; the question and
+    # its answer(s) are blank-line separated, and the sections too.
+    assert "open.push(m.text)" in fn_body
+    assert 's.answers.join("\\n\\n")' in fn_body
+    assert '.join("\\n\\n")' in fn_body
+    # ALL trailing whitespace collapses to a single final newline.
+    assert 'body.replace(/\\s+$/, "") + "\\n"' in fn_body
+    # Only raw text travels: no record field beyond who/text is read.
+    assert "m.thinking" not in fn_body
+    assert "m.sources" not in fn_body
+    assert "m.deflected" not in fn_body
+    assert "m.tools" not in fn_body
+    # saveAsDoc POSTS the transcript as the body (and the dead
+    # single-bubble markdown argument is gone from its signature).
+    save_idx = js.find("async function saveAsDoc(btn) {")
+    assert save_idx > fn_idx, "saveAsDoc missing (or still carries markdown)"
+    save_body = js[save_idx : save_idx + 3000]
+    assert "body: buildSessionTranscript()" in save_body
+    assert "markdown" not in save_body
+
+
 def test_app_js_post_payload_and_navigation() -> None:
-    """Click → POST /api/doc-drafts {title, path, body: markdown} (the
-    raw markdown is the body — never HTML) → 201 →
+    """Click → POST /api/doc-drafts {title, path, body: the
+    FULL-SESSION transcript} (phase 75 A6 — every Q/A up to the click,
+    in order — never HTML) → 201 →
     location.assign("/doc-edit.html?draft=" + token). A double-click
     guard disables the button until the outcome (released in the
     finally — never stale); failure shows the neutral one-line banner
     (phase-55 convention) and never navigates."""
     js = _text(APP_JS)
-    fn_idx = js.find("async function saveAsDoc(btn, markdown) {")
+    fn_idx = js.find("async function saveAsDoc(btn) {")
     assert fn_idx != -1, "saveAsDoc missing"
     fn_body = js[fn_idx : fn_idx + 3000]
     assert 'fetch("/api/doc-drafts"' in fn_body
-    assert 'JSON.stringify({ title, path, body: markdown })' in fn_body
+    assert "body: buildSessionTranscript()" in fn_body
     assert 'location.assign("/doc-edit.html?draft=" + draft.token)' in fn_body
     assert "btn.disabled = true" in fn_body
     assert "btn.disabled = false" in fn_body