fix(kyberforge): apply cross-skill audit findings to skill factory trio

- validate.sh: move FAIL lines and failure summary to stdout; stderr
  reserved for fatal script errors only (missing SKILL.md, bad args)
- skill-audit SKILL.md: replace concrete plugins/kyberforge/skills/...
  example with abstract placeholder to fix meta-circularity
- skill-write SKILL.md: rephrase placeholder section-heading instruction
  to remove embedded FILL IN: from a code span, clearing validator false positive
- skill-improve SKILL.md: wrap Step 2 root-cause example in a text fence
- skill-write assets/templates/README.md: update Files table to individual-
  file rows so skill-audit can verify per-file coverage

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plugins/kyberforge/skills/skill-improve/SKILL.md

@@ -39,11 +39,13 @@ Read the current skill files (SKILL.md and any files in scripts/, references/, a
 
 Group signals by **root cause**, not symptom. Ask: "What single gap in the skill causes this cluster of failures?" One root cause → one fix. Do not make a separate edit for each symptom.
 
+```text
 Example:
 - Eval fails because output format is wrong
 - Audit finding: no output template defined
 - User feedback: "I always have to ask it to format the output"
-- Root cause: SKILL.md has no output format specification → one fix: add an output template
+→ Root cause: SKILL.md has no output format specification → one fix: add an output template
+```
 
 ## Step 3 — Announce planned changes