meta: bind Zod schemas for webhook / connector / sharing_rule WITHOUT registering the kinds — close the unvalidated PUT /meta write hole (#2657 audit, option A) #6245

Split from the #2657 coverage audit (#6234, 2026-08-07) as the unconditional first step — restore-invariant class, compatible with whichever way the maintainer later rules the admission question (B/C) on #2657.

The hole (today, on main)

webhook, connector and sharing_rule stack collections are already writable through PUT /meta with zero schema validation — a spec-invalid webhook body stores and answers success: true. Proven by the repo's own test: packages/objectql/src/protocol-meta.test.ts:1461-1469 saves an invalid webhook and expects success (that pin flips with this fix). This is the same enforced-but-undeclared shape #5271 closed for api.

The fix (size S)

Bind the three kinds' Zod schemas via registerMetadataTypeSchema (metadata-type-schemas.ts:183) — exactly the #5271 mechanism — without registering them as metadata kinds (no registry entries, no new capability surface, no authorization change). Effects:

• a wrong body fails loudly at the existing door (422) instead of storing garbage;
• the registry-driven Metadata Directory upgrades from raw-JSON to a real form for free;
• the Studio metadata coverage gaps: surface remaining types + promote un-typed concepts #2657 admission ruling stays fully open — this card neither presumes B nor C.

Caveats (from the audit, follow the precedents)

• Author-shape vs stored-shape envelope: sharing_rule's schema is .strict() with no envelope — stamped/stored rows would fail a naive parse; follow the [spec] api 补进 DEFAULT_METADATA_TYPE_REGISTRY 与 BUILTIN_METADATA_TYPE_SCHEMAS(#5206 第 1 步,拆单) #5271/feat(spec): api 补进 DEFAULT_METADATA_TYPE_REGISTRY 与 BUILTIN_METADATA_TYPE_SCHEMAS (#5271) #5312 lesson (validate the author shape at the write door; do not reject stamped rows).
• connector: pick the binding target deliberately (ConnectorSchema vs DeclarativeConnectorEntrySchema) and record why in the PR.
• Flip the protocol-meta.test.ts:1461 pin to assert the 422 (it currently pins the hole).

Release-board note: criterion ① (an authoring surface that stores arbitrary invalid bodies today) — same class as #5961, which is on the board; target:v17 applied accordingly, triage seat may veto.

Related

#2657 (admission ruling B/C, pending) · #6234 (the audit) · #5271 / #5312 (the api precedent pair) · #6242 (enumeration-drift finding, adjacent)