feat(docs): add offline documentation, config_help viewer, and CI pipelines

- docs/fish-config.md: curated terminal-optimized manual covering all
  public functions, keybindings, abbreviations, configuration variables,
  dependency catalog, and customization guide. Written for ov/bat/less
  readability rather than browser rendering — no callouts, no hyperlinks.
  Pandoc-compatible YAML front matter for man page compilation.

- functions/config_help.fish: viewer function with fallback chain
  ov -> bat -> man -l -> less -> cat. Accepts an optional section
  keyword to jump directly to the first matching heading.

- .gitea/workflows/man-page.yml: compiles docs/fish-config.md to
  docs/fish-config.1 via pandoc on every push to main that touches the
  source doc, then commits the result automatically.

- .gitea/workflows/docs-drift.yml: opens a reminder issue whenever
  README.md changes without a corresponding docs/fish-config.md update
  in the same push.

- README.md: documents config_help and the offline manual.
- AGENTS.md: adds Convention 10 requiring offline doc to be updated
  alongside any function, keybinding, or config change.

.gitea/workflows/docs-drift.yml

@@ -0,0 +1,45 @@
+name: Offline docs drift reminder
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'README.md'
+
+jobs:
+  remind:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 2
+
+      - name: Check whether offline doc changed in same push
+        id: drift
+        run: |
+          if git diff --name-only HEAD~1 HEAD | grep -q '^docs/fish-config\.md$'; then
+            echo "synced=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "synced=false" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Open drift reminder issue
+        if: steps.drift.outputs.synced == 'false'
+        uses: actions/gitea-issue-create@v1
+        with:
+          token: ${{ secrets.GITEA_TOKEN }}
+          title: "docs: README updated — review docs/fish-config.md for drift"
+          body: |
+            README.md was modified in commit ${{ github.sha }} but
+            `docs/fish-config.md` (the offline manual) was not updated in
+            the same push.
+
+            Please review the README diff and update the offline documentation
+            if any functions, keybindings, abbreviations, or configuration
+            options were added, removed, or changed.
+
+            Commit: ${{ github.sha }}
+            Branch: ${{ github.ref_name }}
+          labels: documentation

.gitea/workflows/man-page.yml

@@ -0,0 +1,37 @@
+name: Generate man page
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'docs/fish-config.md'
+
+jobs:
+  build-manpage:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          token: ${{ secrets.GITEA_TOKEN }}
+
+      - name: Install pandoc
+        run: sudo apt-get update -qq && sudo apt-get install -y pandoc
+
+      - name: Compile man page
+        run: |
+          pandoc --standalone \
+                 --from markdown \
+                 --to man \
+                 docs/fish-config.md \
+                 -o docs/fish-config.1
+
+      - name: Commit man page
+        run: |
+          git config user.name  "Gitea Actions"
+          git config user.email "actions@gitea"
+          git add docs/fish-config.1
+          git diff --cached --quiet && echo "No changes to commit" && exit 0
+          git commit -m "chore(docs): regenerate fish-config.1 man page"
+          git push