docs: purge stale/redundant docs; drop prebuilt/ (src/code is the single source)

[SethMorrowSoftware]

A documentation-and-cruft cleanup pass after a thorough repo review. Three Opus
audits (plans/archive, reference docs, root/meta) plus a build-pipeline + asset
pass. The headline finding: the docs are in good shape — almost nothing was
truly deletable, so this is targeted cleanup, not a mass purge.

prebuilt/ removed — src/code/ is now the single committed source

prebuilt/ held byte-identical copies of the libraries already committed under
src/code/<arch>-<platform>/ (the tree that actually ships inside the extension) —
the same 2.3 MB committed twice. Removed prebuilt/; src/code/ is the one source.

• Rewrote tools/package-extension.py: it no longer assembles src/code/ from a
  prebuilt/ default. src/code/ is committed (built/tested by CI, attached to each
  Release); the script now refreshes a platform from an explicit
  --linux64/--win64/… path, and --check lists/validates the committed tree.
• Repointed every prebuilt/ reference (CLAUDE.md, docs/building.md,
  getting-started.md, architecture.md, platformer-polish-plan.md,
  tools/make-release.py). The loose-library dev fallback now copies from
  src/code/<arch>-<platform>/box2dxt.* (already bare-named).

CHANGELOG.md — cut a real release (1,979 → 207 lines)

Rolled the ~1,960-line single [Unreleased] dev-log into a tagged
[0.3.0] - 2026-06-22, merged the duplicate Added/Fixed blocks into one
Added/Changed/Fixed/Removed set, condensed each entry to a one-line headline
(no entry dropped — 167 headlines preserved), and removed the dead compare links
(no v0.2.0 tag ever existed).

docs/asset-expansion-plan.md — trimmed the abandoned roadmap

Cut Phases H–J (not pursued) and the contradictory all-unchecked "definition of
done" checklist down to short notes; kept the A–G as-built record.

Doc accuracy fixes

• kit-reference.md: TOC now lists all 22 sections (was 11 — the whole Game Kit
  half was unnavigable); added the missing b2kLayerBits row.
• kit-guide.md: fixed the off-by-one Contents (added the missing "21. Player
  actions" entry, renumbered 22/23, fixed two broken anchors); corrected
  b2kPlayerAnims to its real 11 parameters.
• docs/archive/*: fixed link-rot to ../plan.md → ../../plan.md (broke when the
  files were moved into archive/).
• spike-gamekit header: docs/game-engine-spec.md → docs/archive/game-engine-spec.md.
• CLAUDE.md: Kit handler count 312 → 313.

Verification

Static gates clean: check-livecodescript.py, sync-embedded-kit.py --check,
package-extension.py --check, plus a full intra-/cross-doc link scan (0 broken
local links). No Kit source changed, so no harness bump.

Deferred (your call — not done here)

• Unused spritesheets (~1.4 MB, 45 files). Zero references from any example;
  asset-expansion-plan.md §1 catalogs them as the dormant library for the now-frozen
  Phases H–J, so they're a deliberate reserve, not accidental cruft. You chose
  list, don't delete — the families are: *-double (8 files), alien* (12),
  *_sheet (10), spritesheet_* (13), plus spritesheet.png/.xml (the city set).
• Tag/publish a v0.3.0 Release so the CHANGELOG section becomes a real release
  and the ../../releases links resolve (also lets CI attach binaries).
• dist/INSTALL.md "Plateformer" — likely a typo, but it's baked into
  make-release.py's defaults too, so left for you to confirm before a cross-file rename.

🤖 Generated with Claude Code

https://claude.ai/code/session_01KcQmrtT7Vun4pwnkvHbhxX

---

Generated by Claude Code