[story-verifier-api] REST API — serve proof verification by sessionId

[Blockchain-Oracle]

Source of truth: context/docs/stories/story-verifier-api.md.
The body of this issue mirrors the story file. If they disagree, the story wins (see SOURCE_OF_TRUTH.md + REFERENCE_REPO_AUDIT.md).

Dependency issues: #9, #8

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Epic: Epic 5 — Verification Dashboard
Estimated time: ~1.5h
Dependencies: story-session-mint, story-tee-proof-flow

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Narrative

As a dashboard developer, I need a verification API that resolves a token ID into session metadata, storage content, and proof status so the UI can render a single trustworthy proof view.

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Acceptance criteria

Given `apps/dashboard/src/app/api/verify/[tokenId]/route.ts` is created
And the route can read chain + storage configuration from environment variables
When a valid GET request is sent to `/api/verify/42`
Then it returns HTTP 200
And the JSON body contains:
  - tokenId
  - sessionId
  - rootHash
  - entryCount
  - verified
  - entries[]

Given `/api/verify/[tokenId]` receives a tokenId that does not exist
When the request is executed
Then it returns HTTP 404
And the response body includes a machine-readable error code

Given a stored session log contains at least 1 tool_call entry
When the API resolves the proof chain
Then `entries.length >= 1`
And at least one entry includes tool, ts, inputHash, and outputHash fields

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File modification map

Create:

• apps/dashboard/src/app/api/verify/[tokenId]/route.ts — GET endpoint for proof resolution
• apps/dashboard/src/lib/verify-proof.ts — helper for chain/storage/proof lookup
• apps/dashboard/tests/verifier-api.test.ts — API tests for success, not found, malformed response

Update:

• apps/dashboard/src/lib/client.ts — add fetch wrapper for verify endpoint calls

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Shell verification

pnpm --filter=dashboard vitest run verifier-api.test.ts
# Must exit 0