fix: restore contract-set regression coverage and mirror canonical problem bounds

release-manifest.test.ts's fixture derived manifest.contractSet.packages
from EXPECTED_CONTRACT_SET_PACKAGES itself, so the equality it checked was
satisfied by construction and CONTRACT_SET_PACKAGE_MISSING became
unreachable from any test in the repo. Adds two independent checks: a
literal (not derived) assertion that EXPECTED_CONTRACT_SET_PACKAGES really
contains @tech-log/studio-contract@2.0.0, and a negative test with a
manifest that omits a package the real expected set requires, asserting
CONTRACT_SET_PACKAGE_MISSING. Confirmed the negative test has teeth by
temporarily disabling the missing-package branch in
verifyContractSet (src/contracts/contract-set.ts) and observing the test
fail before reverting.

Also narrows tech-log-studio-contract-contribution.ts's problemSchema to
match canonical ProblemDetails exactly: title max 200 (was 240) and type
unbounded (was max 512; canonical only constrains it as
format: uri-reference). Both prior values were over-permissive, so no
previously-accepted document is now rejected.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/features/tech-log/contracts/tech-log-studio-contract-contribution.ts

@@ -47,8 +47,9 @@ const passthrough = <T>(schemaId: string) =>
 
 const problemSchema = z
   .object({
-    type: z.string().min(1).max(512),
-    title: z.string().min(1).max(240),
+    // canonical: `format: uri-reference` only, no length bound.
+    type: z.string().min(1),
+    title: z.string().min(1).max(200),
     status: z.int().min(400).max(599),
     detail: z.string().min(1).max(5000),
     code: z.enum(STUDIO_ERROR_CODES as unknown as [string, ...string[]]),