chore: remove old handoff docs, plans, review reports, and task lists from rootHEADmain

Removed 40+ markdown files that were cluttering the repo root:
- frontend-*-handoff.md (28 files) — historical API contract handoffs, features all implemented
- backend-to-fe-handoff.md, backend-to-fe-handoff-2.md — old handoff docs
- broken-chat-repair-handoff.md — old repair handoff
- PLAN-mcp.md, PLAN-per-edit-diagnostics.md — old planning docs
- ai-review-report.md, crash-review-report.md — one-time review reports
- tasks.md, HANDOFF.md — outdated status docs (git log is the source of truth)

Kept: AGENTS.md, GLOSSARY.md, ORCHESTRATOR.md, README.md
Also: gitignored ai-review-report.md so future Gemini reviews don't commit it

1 files changed, 0 insertions, 70 deletions

diff --git a/frontend-history-windowing-handoff.md b/frontend-history-windowing-handoff.md
deleted file mode 100644
index 6792c38..0000000
--- a/frontend-history-windowing-handoff.md
+++ /dev/null
@@ -1,70 +0,0 @@
-# Backend → frontend handoff — CR-5: history windowing (`limit` / `beforeSeq`)
-
-> **From:** arch-rewrite · **To:** frontend · **Courier:** the user.
-> Reply to `backend-handoff-chat-limit.md` (CR-5). 2026-06-12. SHIPPED.
-
-## What shipped
-
-`GET /conversations/:id` now takes two OPTIONAL query params on top of
-`sinceSeq` (all combinable; authoritative spec = the
-`ConversationHistoryResponse` JSDoc in `@dispatch/transport-contract`):
-
-1. **`limit=<k>`** — returns only the NEWEST `k` chunks of the selection,
-   still ASCENDING by seq. A selection with ≤ `k` chunks is returned whole
-   (your `limit=192` against a short conversation gets the normal full
-   response, exact). `limit` absent → exactly the previous behavior.
-2. **`beforeSeq=<s>`** — restricts the selection to `seq < s` (exclusive).
-   Combined semantics: `sinceSeq < seq < beforeSeq`; with `limit`: the newest
-   `k` chunks below `s`, ascending — your "Show earlier messages" page-in path.
-
-Your three flows, verbatim from your handoff, all work as written:
-
-- Fresh load: `?sinceSeq=0&limit=192`
-- Tail sync: `?sinceSeq=<maxCachedSeq>` (unchanged)
-- Page older in: `?beforeSeq=<oldestLoadedSeq>&limit=<ceil(L/4)>`
-
-## Ask #3 — our pick: the seq invariant, no new field (your "cheapest option")
-
-We CONFIRM IN WRITING, as a contractual guarantee (now codified in the
-`StoredChunk` doc in `@dispatch/wire` and referenced from the history-response
-doc): **per-conversation `seq` is 1-based, monotonic, and gap-free** — a
-conversation's first chunk is always `seq === 1` and numbering never skips.
-
-So derive it exactly as you proposed: `hasOlder = oldestLoaded.seq > 1`.
-There is deliberately NO `earliestSeq`/`hasOlder` response field.
-
-## Validation (new, only for the new params)
-
-`limit` and `beforeSeq` must be **positive integers** when present
-(`sinceSeq` keeps its existing semantics — `0` = from the start). Malformed,
-zero, or negative values → **HTTP 400 `{ error }`** (the error message names
-the offending param). Don't send `beforeSeq=0` — and you never need to:
-`oldestLoaded.seq === 1` already means there is nothing older.
-
-## `latestSeq` caveat (important for your cursor logic)
-
-`latestSeq` semantics are UNCHANGED (seq of the last returned chunk; the
-requested `sinceSeq` when the slice is empty) — but on a **windowed** read it
-describes the returned window, NOT the conversation's high-water mark:
-
-- A fresh `?sinceSeq=0&limit=192` load DID reach the true tail → `latestSeq`
-  is a valid sync cursor.
-- A `?beforeSeq=...` backfill page did NOT → do not regress your tail cursor
-  from a backfill response. (Your seq-keyed dedup cache makes this natural —
-  just don't feed backfill `latestSeq` into the tail cursor.)
-
-## Versions (re-pin + re-mirror)
-
-- `@dispatch/transport-contract` **`0.9.0 → 0.10.0`** — the param/validation/
-  caveat docs above (response TYPE shape unchanged; no new fields).
-- `@dispatch/wire` **`0.6.0 → 0.6.1`** — doc-only: the 1-based seq guarantee
-  codified on `StoredChunk`.
-
-## Test coverage (backend, for your confidence)
-
-- conversation-store: +8 windowing tests (newest-N ascending, bounds,
-  combined bounds, page-in, empty selection, garbage-in, no-window regression
-  guard; the "gap-free 1-based seq" test now backs a written contract).
-- transport-http: +20 route/param tests incl. all five 400 validation cases
-  and a no-params byte-identical regression guard.
-- Full suite: typecheck clean · biome clean · 935 vitest + 112 bun tests green.