fix: un-ignore corpus/ and tag commits as morpheus-docs-refresh

Two cosmetic + functional fixes carried over imperfectly from the
template / hvm-docs clone:

1. .gitignore was over-ignoring corpus/. PLAN.md's design has the
   corpus committed (so image-only.yml can build images without
   re-scraping). Run 109 hit the same silent `git add corpus` no-op
   HVM hit on its first refresh; fixing now to unblock the build.

2. The refresh workflow was tagging commits as "hvm-docs-refresh"
   because the workflow was copied wholesale from hvm-docs. Renamed
   to "morpheus-docs-refresh" so the git log makes sense.

chroma/ and bm25/ stay ignored — those are rebuilt by
`python -m rag.index --rebuild` at CI time.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -2,11 +2,17 @@
 venv/
 .venv/
 
-# Regenerable from corpus + CI
+# Indexes are regenerated from corpus by `python -m rag.index --rebuild`
-corpus/
+# (run in CI before docker build). Don't commit them.
 chroma/
 bm25/
 
+# corpus/ IS committed — the weekly refresh workflow writes scraped
+# pages here and `git add bundles.json corpus`s them. Same fix HVM hit
+# on its first refresh (PR #1) — template's .gitignore over-ignored
+# corpus/ which silently dropped the add and the workflow always
+# reported "no changes".
+
 # Python detritus
 __pycache__/
 *.py[cod]