feat(client): serve conversation workspace static files

[VascoSch92]

Summary

Split from #231 (one feature per PR). Adds client coverage for the agent-server's static workspace-serving routes, which the audit reported as missing.

Endpoint	Status before	Change
GET /api/conversations/{id}/workspace	missing	new ConversationClient.getWorkspaceRoot()
GET /api/conversations/{id}/workspace/{path}	missing	new ConversationClient.getWorkspaceFile()

Details

• Both methods return the raw bytes as a Blob (call .text() for HTML/text) so binary artifacts survive intact, matching FileClient.downloadTrajectory.
• getWorkspaceRoot serves the workspace root index.html; getWorkspaceFile serves a workspace-relative file (nested paths supported). The agent-server only serves local workspaces — non-local workspaces, a missing directory/file, or the absence of index.html yield 404; path traversal is rejected with 400.

Testing

• Unit (src/__tests__/api-clients.test.ts, mocked fetch): both routes are GET, return a Blob, and round-trip text content; asserts the exact URLs (including the nested path).
• Integration (deterministic-api.integration.test.ts): writes a root index.html and a nested file into the mounted workspace, serves both back verbatim through the static routes, and asserts 404 for a missing file.
• npm run build, lint (0 errors), and format:check pass; full unit suite green.

[github-actions]

Endpoint audit

❌ 8 off-contract call(s) — not on the agent-server · classifiers: cloud

Category	Count
❌ Off-contract (not on agent-server)	8
⛔ no known backend	7
↗️ served by cloud	1
➕ Missing API (agent-server has, client lacks)	7
agent-server endpoints	112
client endpoints	111

❌ Not on agent-server (gated, 8)

⛔ (no known backend) — served by no backend we can see (7)

• DELETE /api/meta-profiles/{}
• GET /api/meta-profiles
• GET /api/meta-profiles/{}
• POST /api/cloud-proxy
• POST /api/meta-profiles/{}
• POST /api/meta-profiles/{}/activate
• POST /api/skills/installed/{}/update

↗️ served by cloud (1)

• GET /api/shared-events/search

➕ Missing API — agent-server exposes it, client does not implement (7)

• GET /
• GET /api/bash/bash_events
• GET /api/conversations
• GET /api/conversations/{}/events
• GET /api/init
• POST /api/init
• POST /api/skills/installed/{}/refresh