feat: repoint MCP tools and UI project calls to core

[geoffjay]

Update MCP run_list_projects and run_get_project tools to target the core service URL (/api/v1/projects). Add core_url to AgentdMcpConfig (env: AGENTD_CORE_URL) and AgentdClient. Create ui/src/services/core.ts with a CoreClient and update ProjectPicker to use it. Remove agent_count/workflow_count from ProjectDetail since core does not compute them.

Closes #1312

[geoffjay]

Review: feat: repoint MCP tools and UI project calls to core

Stack position: This PR (issue-1312) is stacked on issue-1311 (PR #1328). PR #1328 was just given a needs-rework label in its own review. This PR's code is clean and correct, but it cannot merge until #1328 is addressed and its fixes propagate up the stack.

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Non-blocking: stale JSDoc comment in ProjectPicker.tsx

The file-level comment at lines 1–4 still describes the component as fetching from the orchestrator:

/**
 * ProjectPicker — dropdown that lists all projects from the orchestrator and
 * lets the user select one as the active knowledge context.
 */

Should be updated to reference core now that the import switched from orchestratorClient to coreClient. Easy one-liner fix.

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Non-blocking: no integration test coverage for the new core routing

tests/common/mod.rs correctly adds core_url: "http://127.0.0.1:1".to_string(), // unused to the test client so it compiles, but run_list_projects and run_get_project have no integration tests against a mock core server. This gap predates this PR — the functions weren't tested before either — so it's not a regression, but a follow-up test using a mock_core_server() modelled on the existing mock_orch_server() would be worthwhile.

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Looks good

• ENV var naming is consistent. AGENTD_CORE_URL in the MCP crate and AGENTD_MCP_CORE_URL in common config follow the exact same pattern used for all other services (AGENTD_ORCHESTRATOR_URL / AGENTD_MCP_ORCHESTRATOR_URL, etc.). No inconsistency.
• URL construction is correct. CoreClient sets baseUrl = serviceConfig.coreServiceUrl (default http://localhost:17000) and each method appends /api/v1/projects. ApiClient constructs the final URL as ${this.baseUrl}${path} → http://localhost:17000/api/v1/projects. ✓
• withAuth pattern followed correctly. CoreClient matches the established pattern used by every other service client (ask, communicate, knowledge, monitor, memory). ✓
• ProjectDetail cleanup is correct. After removing agent_count/workflow_count, the struct has id, name, description, created_at, updated_at — which exactly matches the core ProjectResponse fields. Serde deserialization will work without any extra attributes needed. ✓
• MCP config wiring is complete. AgentdMcpConfig::from_env(), ValidateConfig, Default, the env-clear lists in all three tests, and test_validate_bad_url_fails are all updated consistently. ✓
• orchestratorClient.listProjects is now dead code in the UI (line 324 of orchestrator.ts has no remaining callers after this PR). Not a problem for this PR but worth a follow-up cleanup.