feat(opencode): add single session status endpoint

[YOMXXX]

Issue for this PR

Closes #29166

Type of change

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

What does this PR do?

Adds GET /session/:sessionID/status for clients that need one session's runtime status without fetching and filtering the full /session/status map.

The endpoint follows the existing /session/:sessionID/... resource shape and delegates to SessionStatus.get(sessionID), so idle sessions return { "type": "idle" }. The OpenAPI scenario and generated JS SDK were updated; the v2 SDK now exposes session.getStatus(...).

How did you verify your code works?

• PATH="$HOME/.bun/bin:$PATH" bun test test/server/httpapi-session.test.ts -t "serves read routes"
• PATH="$HOME/.bun/bin:$PATH" bun test test/server/httpapi-session.test.ts
• PATH="$HOME/.bun/bin:$PATH" bun run script/httpapi-exercise.ts --mode coverage --fail-on-missing --fail-on-skip
• PATH="$HOME/.bun/bin:$PATH" bun run test:httpapi
• PATH="$HOME/.bun/bin:$PATH" bun typecheck from packages/opencode
• PATH="$HOME/.bun/bin:$PATH" bun typecheck from packages/sdk/js
• git diff --check
• PATH="$HOME/.bun/bin:$PATH" bun ./packages/sdk/js/script/build.ts

I also ran .husky/pre-push; it failed in the unrelated @opencode-ai/console-support package because local dependencies/types such as @solidjs/meta, @solidjs/router, solid-js, vite, and generated @opencode-ai/console-core/... modules were missing. The opencode and SDK checks above passed.

Screenshots / recordings

N/A - HTTP API and SDK change only.

Checklist

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

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential Duplicate PRs Found

PR #29244: feat(api): add single-session status HTTP endpoint

• feat(api): add single-session status HTTP endpoint #29244
• This appears to be addressing the same feature: a single-session status HTTP endpoint

PR #29165: fix(opencode): expose single session status endpoint

• fix(opencode): expose single session status endpoint #29165
• This also targets the same functionality: exposing a single session status endpoint

Both of these PRs appear to be closely related or potentially duplicating the work in the current PR #29421. You may want to review their status and see if they're addressing the same issue #29166 or if they're alternative approaches.