Core sync: wire gaps — discovery maxAttachmentBytes, relatedTo label param, dissociate without DELETE-body, optional timezone (core #56, #69)

[cuibonobo]

Server side of the haverstack/core#56 wire-gap batch plus the config item from haverstack/core#69.

1. Discovery omits maxAttachmentBytes (core #56 item 4)

/.well-known/stack (src/routes/wellknown.ts:8-15) returns version/entityId/timezone/capabilities only. The server has a configured limit and returns 413 past it, but clients can only discover it by burning a full upload. Add maxAttachmentBytes (or null = unlimited) once the spec/AdapterCapabilities field lands.

2. relatedTo label param name (core #56 item 1)

Core #56 adds relatedToLabel to the spec's GET /records param list. This server already implements the concept but under its own name, relatedLabel (src/routes/records.ts:106) — undocumented in the spec, so adapter-api will send a param we ignore, silently widening the query (the exact failure #56 exists to kill). Rename to whatever the spec lands on; conformance fixture pins it.

3. DELETE /records/:id/associations reads a JSON body (core #56 item 3)

src/routes/records.ts:320-326. DELETE bodies have no defined semantics (RFC 9110 §9.3.5) and get dropped by proxies. Core #56 respecs this — likely POST /records/:id/associations/delete or query-param discriminants. Implement the replacement; keep the old route through a deprecation window only if the owner wants one (no install base argues for cutting straight over, per the standing policy).

4. TIMEZONE default pretends knowledge (core #69 item 2)

Core #69 makes timezone optional at init — "default absent, not 'UTC' — a default pretends knowledge." The server's config does exactly the pretending: optional('TIMEZONE', 'UTC') (src/config.ts:32). Make it truly optional passthrough (absent unless set), update .env.example/README, and let discovery omit it when absent.

Also from #56 but requiring no server change: content-filter capability honesty is adapter-api's throw-don't-widen fix; this server declares contentFieldQuery truthfully via stack.features already. The getType-per-write cache is core-side; it will reduce server load for free.

Work items

• Discovery field + capabilities passthrough
• Param rename to the spec'd name
• Dissociation endpoint replacement + docs/api.md
• Optional timezone (config + discovery + docs)
• Fixtures (Core sync: adopt the shared conformance fixtures; fix the PATCH body shape; add the intent-split endpoints (core #52) #32) for all of the above

Refs haverstack/core#56, haverstack/core#69, #32.