fix: preserve resolved prompt permissions

[kocaemre]

Summary

• Preserve the Codex app-server's resolved default approval/reviewer/sandbox settings in session metadata.
• Use those resolved permissions for default Agent prompts instead of reapplying the hardcoded default Agent preset.
• Keep explicit non-default mode behavior unchanged, and continue adding ACP additionalDirectories to workspace-write roots.
• Add regression coverage for configured writable roots/network access and explicit mode overrides.

Closes #477

Test Plan

• npm run typecheck
• npx vitest run src/__tests__/CodexACPAgent/CodexAcpClient.test.ts --testNamePattern 'preserves resolved default prompt permissions|uses explicit non-default mode prompt permissions|applies ACP additional directories'
• npx vitest run src/__tests__/CodexACPAgent/CodexAcpClient.test.ts
• git diff --check

Note: the full targeted test file prints existing stderr log lines from auth/rate-limit negative-path tests, but the Vitest run exited successfully with 107/107 tests passing.

[kocaemre]

Rebased this PR onto current main and resolved the prompt-permission conflicts against the current session resume/load flow.

Verification:

• RED proof: temporarily restored production files to upstream/main while keeping the regression tests; npm run test -- src/__tests__/CodexACPAgent/CodexAcpClient.test.ts -t 'resolved default prompt permissions|explicit non-default mode prompt permissions' failed because default turns lost the resolved reviewer/sandbox/network/writable root values.
• GREEN: npm run test -- src/__tests__/CodexACPAgent/CodexAcpClient.test.ts -t 'resolved default prompt permissions|explicit non-default mode prompt permissions' — 2 passed, 112 skipped.
• GREEN broader file: npm run test -- src/__tests__/CodexACPAgent/CodexAcpClient.test.ts — 114 passed.
• npm run typecheck — passed.
• npm run build — passed.
• git diff --check upstream/main..HEAD — clean.

Head: 8b229be5d8615a22268a1fd3370e5193c4ca3887.

[kocaemre]

Rebased this onto current main (ca1d971) after it became conflicting again and kept the existing prompt-permission replay behavior while preserving the current MCP/session-failure/auth-status code paths.

Verification on head 038cf410:

• npm ci
• npm run test -- src/__tests__/CodexACPAgent/CodexAcpClient.test.ts -t 'preserves resolved prompt permissions|prompt permissions' — 2 passed, 113 skipped
• npm run test -- src/__tests__/CodexACPAgent/CodexAcpClient.test.ts — 115 passed
• npm run typecheck
• npm run build
• git diff --check upstream/main..HEAD

gh pr view 503 now reports OPEN / MERGEABLE / UNSTABLE; files are still limited to the prompt-permission patch and its tests.