runtime: Claude Code and Gemini resolve session.log and the tps bin dir under the current HOME #822

Follow-up from #810 (round 5). After #810 the fallback SOUL.md path is one helper (getFallbackSoulPath) resolved through homeDir(). Three run-time paths in the other two runtimes still use os.homedir(), which under Bun keeps the start-up HOME: claude-code-runtime.ts ~:159 (default session.log), gemini-runtime.ts ~:126 (default session.log) and ~:134 (~/.tps/bin on the tps shim PATH). The fix moves them to homeDir() (as #810 did for the Codex runtime) with a test that changes HOME after module load and asserts each path, and a mutation back to os.homedir() that turns it red.

Refs #800, #810