feat(610): split the decision corpus into one YAML-frontmatter file per record

168 records -> docs/decisions/records/<area>/<topic>.md (163 active, 23 dirs) and
docs/decisions/archive/<area>/<topic>.md (5 archived). The filename IS the key,
so one-active-record-per-key becomes a filesystem property rather than a
validator check, and supersession becomes a `git mv`.

WHY: the monolith was a concurrency problem before an aesthetic one. A
3,900-line append target made parallel sessions collide -- PR #605 and PR #614
both hit append-vs-append conflicts during routine rebases, and hand-resolving
those inside the corpus is exactly the operation the rationale-rewrite guard
exists to police.

HOW IT IS VERIFIED: a ~170-file diff cannot be meaningfully read, so correctness
does not rest on reading it. The parser was taught BOTH formats first, so the
body-diff guard parses the old form at the merge-base and the new form at head --
the migration validates itself, no bypass. The proof is a field-level equivalence
harness: 168 records before and after, zero lost, zero gained, zero field
mismatches, zero rationale bodies differing. Reviewers should scrutinise the
harness; it is the actual evidence.

What measuring caught that reading would not have:

- ~500 lines sit OUTSIDE any record -- decisions.md's lifecycle schema and each
  topic file's preamble, mostly the only copy. Source files are kept and
  stripped, never deleted. They also cannot be filed per-area: topic files hold
  several areas and 4 of 23 areas span several files.
- Archive discovery was a non-recursive glob; after the split it found ZERO
  archived records, surfacing as four bogus "supersedes points to unknown key"
  errors rather than an obvious failure.
- ~32 live docs point into the corpus BY DATE, which the split dangles. Each
  stripped file now ends with a generated "Records formerly in this file" index,
  which also rescues the identical breadcrumbs in old issue comments.
- decisions.md's "In this file:" list was 97 same-file anchor bullets that the
  split makes WRONG, not merely stale. Dropped; the generated index replaces
  them with links that resolve.

The equivalence harness now runs against a checked-in FIXTURE, not the live
corpus. The earlier version migrated the real tree, which made it a one-shot:
the moment the migration landed there was nothing left to move and the tests
failed for reasons unrelated to the code. A fixture keeps them testing the
SCRIPT rather than the repo's current state.

Keys preserved verbatim, warts included: `sched` (12) and `scheduling` (1) remain
two directories for one concept. Renaming a key is not a move -- it changes
identity, breaks the equivalence proof, and invalidates MemPalace's per-key
drawers. Taxonomy normalisation is separate work.

refs #610

docs/decisions/records/security/contract-freeze-honesty.md

@@ -0,0 +1,40 @@
+---
+key: security.contract-freeze-honesty
+title: 2026-07-12 (#197 Bundle C — contract-freeze honesty)
+status: active
+since: '2026-07-12'
+supersedes: none
+superseded-by: none
+rule: The OpenAPI doc's declared security/401 scheme is generated from the same `ApiKeyAuthorizationFilter.EndpointRequiresKey` predicate the runtime enforces (so declared auth can't drift from enforced auth), every `/api/*` action returns a ResponseModel (no raw Application VMs), and Channel REST resources are keyed by immutable `Id`, never mutable `Number`.
+signals: 'OpenAPI contract honesty, ResponseModel wrapping, Id vs Number key · paths: `OpenApiContractHonestyTests`, `ErsatzTV.Core/Api` · issues: #197, #287, #288'
+mechanics: '`OpenApiContractHonestyTests`; `docs/api-conventions.md`'
+---
+
+**#287 — OpenAPI contract honesty by construction.** The "v1" document now emits the `ApiKey` security
+scheme plus per-operation `security`/`401` derived from the *same*
+`ApiKeyAuthorizationFilter.EndpointRequiresKey` predicate the runtime filter enforces, so declared auth
+can never drift from enforced auth. Every operation also gets a synthesized stable `operationId` (the
+framework only assigned one when `Name=` was set — ~90 were missing), and body/param-binding operations
+get the documented `400 ValidationProblemDetails` they actually return. `DayOfWeek` is now a string enum
+in the schema (added to `Startup.UseStringEnumSchemas`), removing the SPA's `WithDayNames` wart. Pinned by
+in-process document generation in tests (`OpenApiContractHonestyTests`) rather than the committed `v1.json`.
+
+**#288 — Wrap the last raw ViewModels; reverse the §7a "intentional `version` leak."** Minted
+`MediaCollectionResponseModel`, `ProgramScheduleResponseModel`, and `ChannelDetailResponseModel` (all
+`#nullable enable`) and routed `CollectionController` / `ScheduleController` / `SmartCollectionController` /
+`ResolutionController.GetResolutionByName` / the channel detail GET+writes through ResponseModels, so no
+`/api/*` action returns an Application VM. This reverses the earlier §7a judgment that a ResponseModel
+"purely to hide one field was disproportionate": `Version` is now header-only (ETag) on every aggregate
+body — confirmed safe by grepping `web/src` (the SPA reads `version` from the ETag header, never the
+response body). `ChannelDetailResponseModel` is the *full editable* field set the channel editor needs
+(distinct from the lean list `ChannelResponseModel`; drops only the derived `webEncodedName`). Also flipped
+`#nullable enable` onto the remaining 24 lagging `ErsatzTV.Core/Api/` files for schema honesty, and added
+`pageNum` paging to `GET /api/search`.
+
+**Channel REST resources are keyed by database `Id`, never by `Number`.** `Channel.Number` is user-mutable
+(editable on update, bulk-renumbered via `/api/channels/bulk/renumber`, transiently invalid mid-renumber),
+so the immutable int PK is the canonical key for all `/api/channels/*` single-item routes, sub-resources
+(including `playout/reset`, re-keyed from `{channelNumber}` to `{id:int}` in Bundle C), and `Location`
+headers. `Number` remains the identity on broadcast surfaces only (IPTV/M3U/XMLTV), a separate contract. A
+number-based lookup endpoint may be added additively later; `UniqueId` (Guid) stays out of the REST
+contract absent a federation requirement.