fix(session): aggregate status across child directories

[noobezlol]

Issue for this PR

Closes #30094

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

GET /session/status only returned status for the selected instance, so sessions running in child project directories were missing when querying from a parent directory. This keeps child-directory status maps available for recursive listing and updates the status handler to include them.

How did you verify your code works?

• reproduced the issue locally
• verified the regression test fails before the fix and passes after the fix
• bun run lint
• bun run --cwd packages/opencode typecheck
• bun test --timeout 30000 test/server/httpapi-sdk.test.ts
• bun run --cwd packages/opencode script/httpapi-exercise.ts --mode effect --include session.status --fail-on-missing --fail-on-skip
• git diff --check
• git diff --cached --check

Screenshots / recordings

Not applicable.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

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