feat: lint reports sections that hold only template placeholders as Unfilled Template Sections (#94)

Files changed:
- CHANGES.md
- EVALS.md
- VERSION
- instructions/wiki-lint/SKILL.md
- instructions/wiki-manage/SKILL.md
- tools/CONTRACT.md
- tools/chemenu/blocks.py
- tools/chemenu/commands/lint.py
- tools/chemenu/evals/scorecard.py
- tools/chemenu/lint_core.py
- tools/chemenu/tests/test_blocks.py
- tools/chemenu/tests/test_evals.py
- tools/chemenu/tests/test_lint.py
- tools/chemenu/tests/test_pipeline_l0.py
- types/type-spec.md

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SnAJ7Z3CpVD3PRbN73QtU2

types/type-spec.md

@@ -233,6 +233,15 @@ between markers by `xref` and `cite`, rendered from frontmatter, and re-rendered
 so scaffolding them would create a section an author is forbidden to edit and the tool would
 replace anyway. See `tools/chemenu/blocks.py`.
 
+**Placeholder text in a template starts with the token `TODO`** - as the whole line or after a
+list marker, checkbox, table cell or bold field label (`TODO: ...`, `- TODO: ...`,
+`- **Version:** TODO (falls zutreffend)`, `| TODO |`), with the token followed by the line end,
+whitespace, `:`, `(`, `)` or `|`. It is a contract, not a habit: `wikitool lint` reports a `##`
+section whose non-blank lines on a page are still all such lines as *Unfilled Template Sections*
+(advisory), and a template that marks its placeholders any other way - an instance-owned one
+included - leaves its unwritten sections invisible to that finding. A single placeholder beside
+written lines is not reported, so a field whose value is genuinely unknown may keep its marker.
+
 ### Ownership boundary
 
 | Owned here | Owned by `kb/CONTRACT.md` | Owned by `kb/CONVENTIONS.md` and the collection contracts |