fix(schema): advertise every tool's outputSchema as permissive (propagates apple-mail-mcp#135)

[sweetrb]

Propagates the schema half of sweetrb/apple-mail-mcp#135 to this repo. Same defect, same fix, verified the same way.

The defect

The MCP client validates a result's structuredContent against the JSON Schema the server advertised — not against the server's own zod object. A bare zod raw shape renders as additionalProperties: false, so any field a handler emits that its schema doesn't enumerate becomes a hard client-side -32602 … data must NOT have additional properties, discarding a payload the handler computed correctly.

The server never notices, because zod's own parse silently strips unknown keys instead of failing. That is exactly why the registerTool/outputSchema migration's "all fields optional, no .strict()" was believed permissive: it covered optionality, it did not cover undeclared keys.

Why it matters here

In apple-mail-mcp this was not latent — it broke get-mail-stats on every call for anyone with IMAP configured, because that tool's IMAP branch spreads an object carrying a perMailbox key the schema never declared. Measuring every repo in the family showed the same advertisement everywhere:

repo	tools advertising additionalProperties: false (before)
apple-mail-mcp	50 of 50 — fixed in 2.10.6
apple-notes-mcp	36 of 36
apple-photos-mcp	21 of 21
apple-numbers-mcp	26 of 26

So in this repo it is currently latent: it costs nothing until some handler's payload gains a key its schema doesn't list, at which point that tool fails completely rather than degrading — and CI would stay green while it happened.

The fix

Every tool registers through a wrapper that wraps its shape in .passthrough(), advertising additionalProperties: true — the contract the migration intended. A declared field still documents the shape; an undeclared one is carried through instead of nuking the result. No tool signature, parameter or behaviour changes.

The guard

The outputSchema contract test now fails any tool advertising additionalProperties: false. The existing assertions couldn't see this class: they check that every tool has a schema and that none requires a field, then round-trip only the diagnostic tools — so a tool with an undeclared key passes CI and fails in the user's client. Verified a real guard rather than a tautology: it reports every tool in this repo as an offender before the fix and none after.

Verification

• typecheck, lint, format:check clean; full unit suite passes
• outputSchema contract suite passes against the freshly built bundle
• Booted the built bundle over stdio and confirmed additionalProperties: false count went to 0
• Committed bundle rebuilt and in sync