Add growth-log skill: methodology for effective learning capture (#2377)

* Add growth-log skill: methodology for writing effective, transferable growth log entries

* Add metadata.origin: ECC frontmatter per repo convention (Greptile feedback)

* Re-sign: apply GPG-verified commit to growth-log branch (rebase artifact, content unchanged)

* docs(growth-log): v1.1.0 — remove personal library structure, generic storage, delivery-gate optional companion

skills/growth-log/SKILL.md

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+---
+name: growth-log
+description: "Use after a complex task, failure, or when reviewing what was learned. Teaches how to write growth logs that extract reusable patterns — not diary entries."
+version: 1.1.0
+metadata:
+  origin: ECC
+---
+
+# Growth Log Skill
+
+> **The problem:** Most people write "fixed a bug in X" as a learning log. That's a diary entry, not a learning artifact. A real growth log extracts the *pattern* so you recognize it next time.
+>
+> **This skill teaches:** How to write learning entries that compound across sessions. Works with any note-taking system — Markdown files, Notion, Obsidian, plain text. Templates are generic; adapt to your setup.
+
+## When to Activate
+
+- After completing a complex task (multi-file, new feature, architecture change)
+- After a failure, mistake, or "that was harder than expected" moment
+- When you want to review what you've learned over a period
+
+**When NOT to activate:** Trivial changes (typo fixes, single-line tweaks, config value changes with no debugging). The threshold: *did this task involve debugging, redoing, rollback, or a non-obvious decision?* If yes → write an entry. If no → skip.
+
+## The Three Rules
+
+### Rule 1: Failures > Achievements
+
+A failure is nutritionally denser than a success. One bug that took 2 hours to find teaches more than 3 features that worked first try.
+
+**Bad:** "Successfully implemented the login flow."
+**Good (web dev):** "Login flow: session token wasn't persisting because the cookie `SameSite` defaulted to `Lax` in Chrome 128+. Pattern: always explicitly set `SameSite=None; Secure` when cross-origin. Signal to recognize: auth breaks after browser upgrade or when crossing origin boundaries."
+**Good (data pipeline):** "CSV import failed silently on empty rows because `pandas.read_csv(dropna=False)` keeps zero-width rows that `len()` counts as valid. Pattern: always `df.dropna(how='all', inplace=True)` before row-count validation."
+
+### Rule 2: The Bole Principle (伯乐原则)
+
+Before writing a new entry, ask: *"Is this fundamentally the same as something I already recorded?"*
+
+Same root cause, different symptom → **merge**, don't duplicate. New root cause → new entry.
+
+**How to check:** Search existing entries for keywords from your root cause before writing. If you find a match, add your new symptom as an additional example under the existing entry rather than creating a duplicate.
+
+**Example:** "Forgot to update the output index after creating a file" and "Forgot to update skill ratings after a task" — same root cause (no automatic capture trigger). Merge into one entry about "post-task capture gaps."
+
+### Rule 3: Must Be Transferable
+
+Every entry must answer: *"Next time I face a similar situation, what do I do differently?"*
+
+If you can't write that sentence, you haven't extracted the pattern yet.
+
+**How to extract a pattern from a concrete event:**
+1. State what happened in one sentence
+2. Ask "why?" iteratively until you reach root cause (usually 3-5 whys)
+3. Generalize: "What class of problem is this?" (not "Chrome 128 bug" but "browser default change breaking existing behavior")
+4. Formulate as: "Next time I see [signal], I will [action]."
+5. Name the signal: what specific observable tells you this pattern is active?
+
+## Entry Template
+
+**Scope:** One entry per distinct root cause. Typical length: 4-8 sentences. If it takes >2 minutes to write, you're narrating events. If <30 seconds, you haven't gone deep enough.
+
+```markdown
+## [Title: the pattern, not the event]
+
+### Context
+- What was I trying to do?
+- What went wrong / what worked surprisingly well?
+
+### Root Cause / Core Insight
+- The underlying mechanism, not just the symptom
+
+### The Pattern (transferable)
+- Next time [similar situation], I will [specific action].
+- Signal to recognize: [what observable tells me this pattern is active?]
+
+### Related
+- [entry-name](../path/to/related-entry.md)
+```
+
+## Entry Types
+
+All four types use the template above. The type determines which sections carry the most weight:
+
+| Type | When to Use | Emphasis | Example Title |
+|------|------------|----------|---------------|
+| **Failure** | Something broke, needed debugging, or required rework | Root Cause | "Config inheritance ≠ behavior inheritance across sessions" |
+| **Methodology** | A repeatable process emerged from the work | Context / Pattern | "PPT → open-book exam study guide: three-layer structure" |
+| **Pattern Discovery** | A reusable insight about tools, systems, or thinking | Pattern section | "PR description template: describe the gap, not the feature" |
+| **Capability Change** | A measurable skill improvement | Context (before vs after) | "Git: from clone/push to independent PR with 12 commits" |
+
+## Quality Checklist
+
+Before finalizing a growth log entry:
+
+- [ ] Does the title name the *pattern*, not the event?
+- [ ] Is there a "Next time I will..." sentence?
+- [ ] Is the "Signal to recognize" specific enough to trigger the pattern next time?
+- [ ] Did I search existing entries for duplicates before writing? (Bole Principle)
+- [ ] Is the root cause distinguished from the symptom?
+- [ ] Are related memories cross-linked?
+- [ ] Is the entry 4-8 sentences? Shorter = too shallow; longer = narrating events.
+
+## Anti-Patterns
+
+- ❌ "Fixed bug in payment module" (event, not pattern)
+- ❌ Copying the git commit message verbatim (commits describe what changed; logs extract why it matters)
+- ❌ Writing an entry for every commit (only when a pattern emerges)
+- ❌ Skipping the transferable sentence (without it, it's just a diary — this is non-negotiable)
+- ❌ Duplicating the same pattern under different titles (violates Bole Principle — search before writing)
+
+## Storage
+
+Store entries wherever you keep notes. Common patterns:
+- Markdown files in a `growth-log/` directory (one file per day: `YYYY-MM-DD.md`)
+- A dedicated section in Notion, Obsidian, or your note-taking app
+- Plain text files with a consistent naming convention
+
+Pick one convention and stick to it. Searchability matters more than format.
+
+## If You Use Delivery Gate
+
+The `delivery-gate` Stop hook checks that learning files were modified today via filesystem timestamps. This skill teaches *what to write* — so the file that delivery-gate checks actually contains useful patterns, not empty timestamps.
+
+```
+Task completes → delivery-gate checks: was the learning file touched today?
+  → Stale (no file modified): block — "what did you learn?"
+  → Fresh (file touched): pass — this skill ensures the content is useful
+```
+
+Having enforcement without methodology → empty entries. Having methodology without enforcement → forgotten captures. Each is independently useful; together they close the loop.