skills(ground-claims): read a past run's code at that run's commit

plugins/tend-ci-runner/skills/ground-claims/SKILL.md

@@ -110,6 +110,25 @@ event, so any workflow it triggered ran and is still in the run list.
 
 ## Recurring hallucination shapes
 
+**A claim about what a past run executed is read at that run's own commit.**
+The checkout is the current default branch; a run from earlier is not. Before
+explaining a failure in terms of a branch, guard, or helper, read the file at
+the run's head, and pin the body's links to that SHA rather than to `HEAD`. A
+fix that landed between the run and the session inverts the reading: the code
+being cited as the cause may be the code added *because* of the failure.
+
+```bash
+SHA=$(gh api "repos/{owner}/{repo}/actions/runs/<id>" --jq .head_sha)
+gh api "repos/{owner}/{repo}/contents/<path>?ref=$SHA" \
+  -H 'Accept: application/vnd.github.raw'
+```
+
+Fetch it rather than reaching for `git show <sha>:<path>`: the checkout holds
+only what a ref reaches, so the head of a squash-merged or deleted branch is
+absent from it, and `git show` then fails into the same wrong answer — the
+`fatal:` goes to stderr while a `| grep -c` downstream prints `0` and exits
+`0`, which reads as "the guard was absent at that run".
+
 **Links must be fetched, not guessed.** Before pasting any URL, run `curl -sI
 <url> | head -1` and confirm `200`. Docs-site slugs are treacherous —
 `escaping.html`, `quoting.html`, and `quote-strings.html` are all plausible;

plugins/tend-ci-runner/skills/post-to-github/SKILL.md

@@ -26,7 +26,7 @@ gh issue comment "$ISSUE" --body-file "$TMPDIR/comment-body.md"
 
 **Line wrapping:** GitHub renders newlines literally in issue bodies, PR descriptions, and comments — a line break in the source becomes a `<br>` in the output, so a paragraph hard-wrapped at ~72 chars ships with mid-sentence breaks. Write each paragraph as a single long line and let the browser reflow. Code blocks, bullet lists, and tables keep their newlines as-is.
 
-**Links.** Always use markdown links for files, issues, PRs, and docs. **Any link containing `#L` must use a commit SHA, never `blob/main/...#L42`** — line numbers shift silently, so the link stays valid but starts pointing at different code than the comment describes. Get the SHA with `git rev-parse HEAD` before composing the link.
+**Links.** Always use markdown links for files, issues, PRs, and docs. **Any link containing `#L` must use a commit SHA, never `blob/main/...#L42`** — line numbers shift silently, so the link stays valid but starts pointing at different code than the comment describes. Get the SHA with `git rev-parse HEAD` before composing the link — except where the body explains a past run, whose links pin to that run's head instead, per **Recurring hallucination shapes** in `/tend-ci-runner:ground-claims`.
 
 - **File-level link (no `#L` anchor)**: `blob/main/src/foo.rs` is fine
 - **Line reference**: `blob/<sha>/src/foo.rs#L42` — commit SHA required, never `blob/main/...#L42`