PR #1308 — Fleet Parity: Enforce --cwd for Grok and -C for Codex with Working-Directory Protection

The Broader Goal at the End of the Previous PR

PR #1306 established the canonical distinction between Workspace Agents (persistent org-chart roles like dev, qa, architect, pm) and Harnesses (swappable model execution backends like Claude, Codex, Grok, Agy, and Local). With that boundary stabilized, the next priority on the roadmap was addressing the remaining fleet-parity vulnerabilities under issue #342.

What Was Missing

In early autonomous development experiments (commit 8c1e124), Agy (Gemini CLI) reset its working directory to an internal scratch path upon launch, ignoring the target git worktree. Because Gemini CLI lacked a command-line --cwd flag, synlynk mitigated this by injecting an explicit ## Working Directory prompt header reminding the model of its required root.

Issue #342 identified that Grok CLI (grok) carries the identical auto-relocation risk (-w, --worktree), yet was completely undefended:

1. synlynk/dispatch.py never passed Grok's native --cwd <CWD> flag.
2. Grok fell into the generic prompt formatter branch without the working-directory reminder.
3. Codex CLI similarly exposed -C, --cd <DIR> to lock its execution root, but was also dispatched without it.

If a harness resets or misinterprets its working root, file edits and tool executions can land silently outside the assigned worktree—a dangerous multi-agent failure mode.

What Shipped

1. Grok Structural Flag & Defense-in-Depth:
   • In synlynk/dispatch.py:dispatch_agent(), dynamically appends ["--cwd", worktree_path] to Grok's execution flags upon worktree creation.
   • Added a dedicated Grok prompt branch in _format_prompt_for_agent() that injects the ## Working Directory reminder header.
2. Codex Working Directory Root:
   • In synlynk/dispatch.py:dispatch_agent(), dynamically appends ["-C", worktree_path] to Codex's execution flags.
3. Comprehensive Test Suite:
   • Added unit test test_format_prompt_for_grok_includes_working_directory in tests/test_synlynk.py.
   • Added unit tests test_grok_dispatch_includes_cwd_flag and test_codex_dispatch_includes_c_flag in tests/test_synlynk.py.
   • Verified that all 499 tests in tests/test_synlynk.py, 107 in tests/test_dispatch.py, and 74 in tests/test_agent_cli.py pass cleanly.