chore(vendor): import pi 1.3.0

Imported as a linear vendor commit so forge rebases do not replay the upstream root tree.

git-subtree-dir: third_party/pi

git-subtree-split: 71023aec1546d6d677a65669c5665c0927ce0dd0

third_party/pi/.pi/prompts/cl.md

@@ -50,5 +50,5 @@ Sections (in order):
 - `### Removed` - Removed features
 
 Attribution:
-- Internal: `Fixed foo ([#123](https://github.com/earendil-works/pi-mono/issues/123))`
-- External: `Added bar ([#456](https://github.com/earendil-works/pi-mono/pull/456) by [@user](https://github.com/user))`
+- Internal: `Fixed foo ([#123](https://github.com/earendil-works/pi/issues/123))`
+- External: `Added bar ([#456](https://github.com/earendil-works/pi/pull/456) by [@user](https://github.com/user))`

third_party/pi/.pi/prompts/dup.md

@@ -0,0 +1,18 @@
+---
+description: Find potential duplicates of a GitHub issue
+argument-hint: "<issue-url>"
+---
+Look for potential duplicates of this issue in its GitHub repo: $1
+
+Steps:
+1. Read the issue with `gh issue view <url> --comments` to understand the problem.
+2. Search open and closed issues and PRs in the same repo with `gh search issues` / `gh issue list --search` / `gh pr list --search`, using several keyword variations (error messages, feature names, affected components, symptoms).
+3. Read promising candidates to confirm they describe the same problem, not just similar words.
+
+A duplicate reports the same problem or requests the same change: same symptom with the same likely cause, or a PR that fixes this exact issue. Sharing a component, an error message, or a related cause is not enough.
+
+Output a short draft GitHub comment with a writte by AI disclosure.
+
+If there are none, reply "No duplicates found."
+
+Do not post, label, or close anything.