[Feature Request] Allow customizable plan file storage location

Bug Description
~/.claude/plans/ に保存されるプランファイルをプロジェクト配下など任意の場所に保存できるように設定できるようにしたい

Environment Info

• Platform: darwin
• Terminal: tmux
• Version: 2.1.1
• Feedback ID: bfd80309-a466-49e1-bd07-54ab035a1790

Errors

[{"error":"Error: {\"message\":\"PeriodicExportingMetricReader: metrics export failed (error Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED 127.0.0.1:4317. Resolution note: )\",\"originalLine\":\"1782\",\"originalColumn\":\"52375\",\"line\":\"1782\",\"column\":\"52375\",\"sourceURL\":\"/$bunfs/root/claude\",\"stack\":\"Error: PeriodicExportingMetricReader: metrics export failed (error Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED 127.0.0.1:4317. Resolution note: )\\n    at _doRun (/$bunfs/root/claude:1782:52375)\\n    at processTicksAndRejections (native:7:39)\",\"name\":\"Error\"}\n    at error (/$bunfs/root/claude:1822:25028)\n    at <anonymous> (/$bunfs/root/claude:206:38485)\n    at qJD (/$bunfs/root/claude:206:39029)\n    at _runOnce (/$bunfs/root/claude:1782:51840)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-01-09T01:59:32.694Z"},{"error":"Error: {\"message\":\"PeriodicExportingMetricReader: metrics export failed (error Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED ::1:4317. Resolution note: )\",\"originalLine\":\"1782\",\"originalColumn\":\"52375\",\"line\":\"1782\",\"column\":\"52375\",\"sourceURL\":\"/$bunfs/root/claude\",\"stack\":\"Error: PeriodicExportingMetricReader: metrics export failed (error Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED ::1:4317. Resolution note: )\\n    at _doRun (/$bunfs/root/claude:1782:52375)\\n    at processTicksAndRejections (native:7:39)\",\"name\":\"Error\"}\n    at error (/$bunfs/root/claude:1822:25028)\n    at <anonymous> (/$bunfs/root/claude:206:38485)\n    at qJD (/$bunfs/root/claude:206:39029)\n    at _runOnce (/$bunfs/root/claude:1782:51840)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-01-09T02:00:32.632Z"},{"error":"Error: {\"message\":\"PeriodicExportingMetricReader: metrics export failed (error Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED ::1:4317. Resolution note: )\",\"originalLine\":\"1782\",\"originalColumn\":\"52375\",\"line\":\"1782\",\"column\":\"52375\",\"sourceURL\":\"/$bunfs/root/claude\",\"stack\":\"Error: PeriodicExportingMetricReader: metrics export failed (error Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED ::1:4317. Resolution note: )\\n    at _doRun (/$bunfs/root/claude:1782:52375)\\n    at processTicksAndRejections (native:7:39)\",\"name\":\"Error\"}\n    at error (/$bunfs/root/claude:1822:25028)\n    at <anonymous> (/$bunfs/root/claude:206:38485)\n    at qJD (/$bunfs/root/claude:206:39029)\n    at _runOnce (/$bunfs/root/claude:1782:51840)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-01-09T02:01:32.638Z"},{"error":"AbortError: The operation was aborted.\n    at unknown\n    at abortChildProcess (node:child_process:935:42)\n    at onAbortListener2 (node:child_process:35:24)\n    at abort (unknown)\n    at <anonymous> (/$bunfs/root/claude:4824:2320)","timestamp":"2026-01-09T02:01:51.398Z"},{"error":"Error: {\"message\":\"PeriodicExportingMetricReader: metrics export failed (error Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED ::1:4317. Resolution note: )\",\"originalLine\":\"1782\",\"originalColumn\":\"52375\",\"line\":\"1782\",\"column\":\"52375\",\"sourceURL\":\"/$bunfs/root/claude\",\"stack\":\"Error: PeriodicExportingMetricReader: metrics export failed (error Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED ::1:4317. Resolution note: )\\n    at _doRun (/$bunfs/root/claude:1782:52375)\\n    at processTicksAndRejections (native:7:39)\",\"name\":\"Error\"}\n    at error (/$bunfs/root/claude:1822:25028)\n    at <anonymous> (/$bunfs/root/claude:206:38485)\n    at qJD (/$bunfs/root/claude:206:39029)\n    at _runOnce (/$bunfs/root/claude:1782:51840)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-01-09T02:02:32.636Z"},{"error":"Error: {\"message\":\"PeriodicExportingMetricReader: metrics export failed

Note: Error logs were truncated.