Reject undeclared editor RPC request fields

[Noisemaker111]

Recovered from the stranded quest worktrees reject-undeclared-fields-on-every-editor-rpc-verb-s7vbgb, verify-real-rpc-behavior-and-local-gates-ndfcd8 and prepare-issue-closing-pr-l996el (all held commit 3fbe0bc, never pushed).

• decodeEditorBridgeRequest rejects any top-level field outside the method's field spec, for every method, with unknown field "<name>" for method "<verb>".
• Declared object payloads (patch, values) stay open.
• Test: every method rejects an undeclared field; the existing lockstep test covers every verb having a field spec.

Root cause: the decoder only type-checked declared fields and ignored the rest, so a misspelt or unsupported field returned ok: true and saved nothing.
Limitation: the MCP stdio path builds requests per tool in toolToBridge, which still drops unknown tool arguments before the decoder sees them.

Closes #1838

Verification

• bun --cwd=packages/editor run test: 256 pass, 0 fail
• bun --cwd=packages/editor run check-types: pass
• bun run ship:preflight: ok
• bun run check-changelog (release note changes/reject-undeclared-rpc-fields-k4w9p2.md): ok
• bun run check-skill-api after gen:skill-api: ok
• CI: all jobs green (one rerun of a 5 s timeout in cli.test.ts bulk import; passes locally and on the first run)
• CLI on tower-guard: --rpc '{"method":"set_marker","id":"x","catalogId":"raider","bogus":1}' → ok:false, $.bogus unknown field "bogus" for method "set_marker"; scene_summary with extra → rejected; plain scene_summary → ok

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