skill-evolution: drop inline provenance markers (#1161)

## Summary
Removes the `<!-- skill-evolution:start --> ... <!-- skill-evolution:end -->` HTML-comment marker requirement for inline edits to existing SKILL.md files. The markers add visible noise that compounds across many small edits, while `git log` / `git blame` already attribute every line to its origin commit. Audit trail now relies on a clear commit subject (e.g. "skill-evolution: add ... to lp-milp-formulation").

Frontmatter `origin: skill-evolution` for new skills and `# origin: skill-evolution` headers for code assets are kept — those edits are creating new files, not editing existing prose.

Distillation checklist updated to remove the marker requirement.

## Testing
- `./ci/utils/validate_skills.sh` passes

## Docs
- Skill content only.

Authors:
  - Ramakrishnap (https://github.com/rgsl888prabhu)

Approvers:
  - Trevor McKay (https://github.com/tmckayus)

URL: #1161

Author: rgsl888prabhu

skills/skill-evolution/SKILL.md

@@ -179,35 +179,11 @@ After inference interactions, review accumulated insights to find patterns.
 
 ## Provenance tagging
 
-Every change made through skill evolution MUST be tagged so its origin is traceable.
+Skill-evolution changes need a traceable origin so a reviewer can find and audit them later. The mechanism depends on what is being added.
 
 ### Updates to existing skills
 
-Wrap added content with **start** and **end** boundary markers so it is easy to locate, review, and remove:
-
-```markdown
-<!-- skill-evolution:start — <short trigger description> -->
-<added content>
-<!-- skill-evolution:end -->
-```
-
-For example, a new table row:
-
-```markdown
-<!-- skill-evolution:start — large objective recursion fix -->
-| Maximum recursion depth | Building big expr with chained `+` | Use `LinearExpression(vars_list, coeffs_list, constant)` |
-<!-- skill-evolution:end -->
-```
-
-Or a new subsection:
-
-```markdown
-<!-- skill-evolution:start — warmstart gotcha -->
-### Warmstart gotcha
-
-Content here...
-<!-- skill-evolution:end -->
-```
+For inline edits to an existing SKILL.md (new bullets, table rows, paragraphs), do NOT wrap content in HTML comment markers. The visible noise compounds across many small edits, and `git log` / `git blame` already attribute every line to the commit that introduced it. Use the commit message and PR description as the audit trail: write a clear commit subject (e.g. "skill-evolution: add large-objective recursion gotcha to lp-milp-formulation") so the origin is greppable in history.
 
 ### New skills
 
@@ -277,9 +253,9 @@ Before proposing, verify:
 - [ ] It does not modify this skill (`skill-evolution`)
 - [ ] It does not expand agent permissions or reduce user control
 - [ ] Code examples do not contain injection patterns (`eval`, `exec`, `os.system` with user input)
-- [ ] Added content is wrapped with `<!-- skill-evolution:start -->` / `<!-- skill-evolution:end -->` markers
 - [ ] New skills have `origin: skill-evolution` in frontmatter
 - [ ] Code assets have `# origin: skill-evolution` header and are runnable
+- [ ] Commit subject starts with `skill-evolution:` so the audit trail is greppable from `git log`
 - [ ] Placed in the single highest-impact skill (common > API > new); not duplicated across skills
 - [ ] Phase is correctly identified (learning/inference/reflection)
 - [ ] Learning-phase proposals include a score; inference-phase proposals are marked unscored