chore: repo-wide cleanup — dead weight, dead code, dedup, slash.ts split

[DBarr3]

Summary

Full-repo audit (3 parallel surveys of src/core/, src/ui/, src/commands/) followed by a bounded, verified cleanup pass — not a rewrite. Every change is either a verbatim move or a mechanical dedup; no behavior changes.

• Dead weight removed: docs/index.html (1.4MB unused bundler placeholder page), web-cloud.png, assets/ (6 files) — all confirmed zero live references.
• Dead code removed: duplicated notYet() helper (zero callers), write-only _lastMediaPrompt state, ~12 dead imports (found via tsc --noUnusedLocals) across slash.ts/media.ts/workflow.ts.
• Duplication consolidated: 5 near-identical fail()/errMsg() error formatters → core/errors.ts (errorMessage/fail), used by media/output/vault/workflow/github command handlers.
• God-file split: commands/slash.ts was 1807 lines (repo's own convention caps files at ~800). Split into a thin dispatcher (522 lines) + 7 concern files (slash_context, slash_git_tools, slash_codegen, slash_hud, slash_vault_workflow, slash_orchestra, slash_media), largest at 303 lines. The handleSlash switch statement stayed physically in slash.ts since test/slash_registry.test.ts parses its raw source text to verify registry↔switch sync.

Docs added:

• scource.md — source-of-truth map: repo structure, canonical-terms glossary, what was fixed, and a precise file:line backlog of what was found but deliberately left alone (and why).
• cleaningnotes.md — full change log, cross-referenced to scource.md.

Independent verification: an adversarial "novice reviewer" subagent (fresh context, told to actively hunt for problems) fact-checked every claim in the two docs against the actual code, then scored the result — Organization 7/10, Quality 9/10, Labeling 7/10, Efficiency 8/10 — and found 4 concrete gaps (missing rows in the ownership table, an off-by-3 line-count claim, unused imports left in already-open files, an undocumented case alias). All 4 are fixed in this PR.

Test plan

• npm run build — clean, 0 errors (tsc --strict)
• npm test — 468/468 pass (re-verified after every batch of changes and again after the post-review fixes)
• tsc --noUnusedLocals --noUnusedParameters --noEmit spot-check confirms the targeted dead imports are gone
• Confirmed zero remaining references to every deleted file (git grep)
• test/slash_registry.test.ts (parses handleSlash's raw switch-case text) still passes after the split
• Manual smoke test of a few /commands in a real REPL session (not run — no live API token in this environment)

🤖 Generated with Claude Code