feat: add pi reviewer support to workflow variants

skills/do-task/claude-code/SKILL.md

@@ -111,6 +111,19 @@ If the user has already specified a reviewer CLI and model (e.g., "do task X, re
 
 Store `REVIEWER_CLI`, `REVIEWER_MODEL`, and `MAX_ROUNDS` for Phases 5 and 8.
 
+Reviewer CLI: `codex`, `claude`, `cursor`, `opencode`, `pi`, or `skip`.
+
+
+If `REVIEWER_CLI=pi`, verify the Pi reviewer binary before entering the review loop:
+
+```bash
+pi --version
+```
+
+For shorthand `pi/<pi-model-name>`, split only on the first slash when the prefix is exactly `pi`; store the complete remainder in `REVIEWER_MODEL`. Examples: `pi/claude-opus-4-7` -> `claude-opus-4-7`, `pi/anthropic/claude-opus-4-7` -> `anthropic/claude-opus-4-7`, and `pi/openrouter/anthropic/claude-opus-4-7` -> `openrouter/anthropic/claude-opus-4-7`.
+
+When `REVIEWER_CLI=pi`, the reviewer model is configured independently from the model running this workflow. If the model/provider is unavailable, surface helper stderr/status and use `pi --list-models [search]` to inspect configured models.
+
 ### Phase 4: Initialize Plan Workspace
 
 **PLAN MODE CHECK:** If currently in plan mode:
@@ -344,7 +357,7 @@ This subroutine is invoked twice per `do-task` run: once in Phase 5 (`REVIEW_KIN
 | `REVIEW_ID` | 8-char hex (from `uuidgen`); reused across rounds of the same loop |
 | `PAYLOAD_PATH` | `/tmp/do-task-${REVIEW_KIND}-${REVIEW_ID}.md` |
 | `PROMPT_TEMPLATE` | `PLAN_REVIEW_PROMPT` or `IMPL_REVIEW_PROMPT` |
-| `REVIEWER_CLI` | `codex` \| `claude` \| `cursor` \| `opencode` |
+| `REVIEWER_CLI` | `codex` \| `claude` \| `cursor` \| `opencode` \| `pi` |
 | `REVIEWER_MODEL` | Model name |
 | `MAX_ROUNDS` | Default 10 |
 | `SESSION_ID_VAR` | `CODEX_PLAN_SESSION_ID` \| `CODEX_IMPL_SESSION_ID` \| `CURSOR_PLAN_SESSION_ID` \| `CURSOR_IMPL_SESSION_ID` \| `OPENCODE_PLAN_SESSION_ID` \| `OPENCODE_IMPL_SESSION_ID` |
@@ -437,6 +450,18 @@ Write the reviewer invocation to `/tmp/do-task-${REVIEW_KIND}-review-${REVIEW_ID
 set -euo pipefail
 ```
 
+
+**If `REVIEWER_CLI` is `pi`:**
+
+Fresh call every round (Pi reviewer calls do not use session resume):
+
+```bash
+pi --no-session --no-skills --no-prompt-templates --no-extensions --no-context-files \
+  --model "$REVIEWER_MODEL" \
+  --tools read,grep,find,ls \
+  -p "Read the file /tmp/do-task-${REVIEW_KIND}-${REVIEW_ID}.md and review. Return exactly the required ## Summary, ## Findings, and ## Verdict structure."
+```
+
 **If `REVIEWER_CLI` is `codex`:**
 
 Round 1 — fresh `codex exec`:
@@ -633,7 +658,7 @@ After the command completes:
   cp /tmp/do-task-${REVIEW_KIND}-review-${REVIEW_ID}.runner.out \
      /tmp/do-task-${REVIEW_KIND}-review-${REVIEW_ID}.md
   ```
-- `claude`: promote `.runner.out` into the `.md` file:
+- `claude` or `pi`: promote `.runner.out` into the `.md` file:
   ```bash
   cp /tmp/do-task-${REVIEW_KIND}-review-${REVIEW_ID}.runner.out \
      /tmp/do-task-${REVIEW_KIND}-review-${REVIEW_ID}.md