docs: cross-platform validation on 5 harnesses (PRI-974)

Tested on Gemini CLI (gemini -p) and Cursor Agent (cursor-agent -p):
- Gemini: Step 0 detection 1/1, Step 1b fallback 1/1
- Cursor: Step 0 detection 1/1, Step 1b fallback 1/1

Both correctly identified no native agent-callable worktree tool,
fell through to git worktree add, and performed safety verification.
Both correctly detected existing worktrees and skipped creation.

5 of 6 harnesses now tested. Only OpenCode untested (no CLI access).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/superpowers/specs/2026-04-06-worktree-rototill-design.md

@@ -306,10 +306,10 @@ As of 2026-04-06, Claude Code is the only harness with an agent-callable mid-ses
 | Harness | Current worktree model | Skill mechanism | Tested |
 |---------|----------------------|-----------------|--------|
 | Claude Code | Agent-callable `EnterWorktree` | Step 1a | 50/50 (GREEN + PRESSURE) |
-| Codex CLI | No native tool (shell only) | Step 1b git fallback | 6/6 on `codex exec` |
+| Codex CLI | No native tool (shell only) | Step 1b git fallback | 6/6 (`codex exec`) |
+| Gemini CLI | Launch-time `--worktree` flag, no agent tool | Step 0 if launched with flag, Step 1b if not | Step 0: 1/1, Step 1b: 1/1 (`gemini -p`) |
+| Cursor Agent | User-facing `/worktree`, no agent tool | Step 0 if user activated, Step 1b if not | Step 0: 1/1, Step 1b: 1/1 (`cursor-agent -p`) |
 | Codex App | Platform-managed, detached HEAD, no agent tool | Step 0 detects existing | 1/1 simulated |
-| Gemini CLI | Launch-time `--worktree` flag, no agent tool | Step 0 if launched with flag, Step 1b if not | Untested (no CLI access) |
-| Cursor | User-facing `/worktree`, no agent tool | Step 0 if user activated, Step 1b if not | Untested (no CLI access) |
 | OpenCode | Detection only (`ctx.worktree`), no agent tool | Step 1b git fallback | Untested (no CLI access) |
 
 **Residual risks:**