Docs: consolidate active planning and archive historical material

The planning package had grown to where a new agent could not tell what was
authoritative. Phase 0 execution prompts sat beside the specification; four
completed milestone reports sat beside the current one; and upstream AI-DnD's
own `plan/` build log and `docs/` project site still described a hosted,
scripted, multi-user product with accounts — every screenshot in it showed a
Scripts tab and a Sign up button, none of which has existed since M2.

`planning/archive/` now holds the history and says so in its own README:
`phase0/` for the research that chose AI-DnD, `milestone-reports/` for M1 and
M2, `decisions/` for ADR 008, the Phase-0-before-build gate Phase 0 satisfied.
`planning/reports/` holds only the current milestone's report, because that is
the one M4 planning has to read; it moves to the archive when M4's replaces it.

Deleted rather than archived: the Phase 0B execution prompts and the
handoff/status/summary documents, the Phase 0A discovery and triage reports,
upstream's `plan/` and `docs/` trees, and `frontend/README.md`, which was Vite's
template boilerplate. All of it is in Git history, and the two recommendation
reports carry every conclusion the deleted research reached.

Archived documents are kept verbatim. Paths written inside them point at where
those files were when the document was written, which is the point: an evidence
record that has been quietly edited is no longer evidence.

Active documentation is corrected where it pointed at the removed trees or
described removed capability as present. `DEVELOPMENT.md`'s "things M1 did not
touch" list had gone stale at M2 and claimed QuickJS scripting was still tested;
its test count was 604 against an actual 638. `README.md` loses the upstream CI
badge, which reported upstream's pipeline rather than this fork's, and a
reference to `backend/app/worldstate/engine.py`, a file that does not exist.
`planning/README.md` is rewritten as the documentation index.

New: `planning/PROJECT-SOURCES.md` and `planning/project-sources.txt`, the
manifest of what belongs in the ChatGPT project's Sources.

Source comments referring to the deleted trees are reworded; no behaviour
changes. 638 backend tests pass, frontend lints and builds, and a reference scan
over all 48 tracked Markdown files reports no unresolved path in active
documentation.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NCbwH7yLGKsj1rhXXzKSCu

planning/BUILD-MILESTONES.md

@@ -97,8 +97,8 @@ A clean production build can start, open the browser UI, generate and persist st
 
 ## Status: COMPLETE
 
-Accepted 2026-09-02. Evidence: `planning/reports/M1-BASELINE-REPORT.md` (run
-logs and packet captures) and `planning/reports/M1-IMPLEMENTATION-REPORT.md`
+Accepted 2026-09-02. Evidence: `planning/archive/milestone-reports/M1-BASELINE-REPORT.md` (run
+logs and packet captures) and `planning/archive/milestone-reports/M1-IMPLEMENTATION-REPORT.md`
 (review report). A01-A06, H01-H03 and H11 all pass on runtime evidence; 648
 backend tests pass, including with no route to the Internet.
 
@@ -168,8 +168,8 @@ The codebase has a narrow single-user/local-only surface and the inherited story
 
 ## Status: COMPLETE
 
-Accepted 2026-09-02. Evidence: `planning/reports/M2-BASELINE-REPORT.md`
-(measurements) and `planning/reports/M2-IMPLEMENTATION-REPORT.md` (review);
+Accepted 2026-09-02. Evidence: `planning/archive/milestone-reports/M2-BASELINE-REPORT.md`
+(measurements) and `planning/archive/milestone-reports/M2-IMPLEMENTATION-REPORT.md` (review);
 verdict *accept with non-blocking debt, proceed to M3*. Implementation is
 commit `8c65ae9`, and the three defects the review found are commit `8652fe7`
 — see the closeout note appended to both reports.
@@ -193,9 +193,10 @@ commit `8c65ae9`, and the three defects the review found are commit `8652fe7`
 **Debt carried forward, none of it blocking M3:** `Settings.model` still
 defaults to `""` with nothing prompting for it (M8); inert legacy tables and
 columns await a cleanup migration once the schema settles, after M3/M5; there
-are still no frontend tests (M8); `docs/*.html`, upstream's project site and not
-served by the app, still links Google Fonts. Full table in the implementation
-report §P.
+are still no frontend tests (M8). `docs/*.html`, upstream's project site, was
+listed here as still linking Google Fonts; the whole inherited `docs/` tree was
+deleted in the 2026-09-03 documentation pass, which closes that item. Full table
+in the implementation report §P.
 
 ---
 
@@ -434,7 +435,7 @@ undo semantics and are expected to be rewritten by M3; that is separate from
 this instrumentation point, and they should likewise be rewritten rather than
 dropped.
 
-Evidence: `planning/reports/M2-IMPLEMENTATION-REPORT.md` §K.2, §Q.
+Evidence: `planning/archive/milestone-reports/M2-IMPLEMENTATION-REPORT.md` §K.2, §Q.
 
 ## Note from M3 — three constraints this milestone must satisfy
 
@@ -529,7 +530,7 @@ M6 therefore additionally requires:
   degraded the storyteller quietly and left the transcript correct, which is the
   right failure direction — but it must also be a *visible* one.
 
-Evidence: `planning/reports/M2-IMPLEMENTATION-REPORT.md` §A.1, §9.1.
+Evidence: `planning/archive/milestone-reports/M2-IMPLEMENTATION-REPORT.md` §A.1, §9.1.
 
 ---