learn-from-fix

# Learn From Fix After fixing a bug or receiving a correction, capture the lesson to prevent future mistakes. ## Usage ``` /phx:learn-from-fix Fixed N+1 query in user listing - was missing preload /phx:learn-from-fix String vs atom key mismatch in params handling /phx:learn-from-fix LiveView assign_async needs render_async in tests /phx:learn-from-fix --library ical --scope personal ICal.to_ics output needs CRLF line endings /phx:learn-from-fix --library ical --scope project Use method: "PUBLISH" for calendar feeds ``` ## Workflow ### Step 1: Verify the Lesson Persist only one of: - A completed fix verified by tests, reproduction, or user confirmation - An explicit rule the user taught or asked to save Stop without writing if neither condition is met. Do not save a hypothesis, unverified workaround, investigation narrative, or unsolved error. Use `/phx:compound` for a detailed completed investigation. Capture the root cause as a concise actionable rule, not the symptom. ### Step 2: Select the Route When both `--library <package>` and `--scope personal|project` are present, use the [Library Route](#library-route). Require both flags; do not guess scope. For the skill directory only, trim surrounding whitespace and lowercase the package name. Preserve underscores when forming directory names (`phoenix_live_view` becomes `hex-phoenix_live_view`). Validate the normalized name against `^[a-z][a-z0-9_]+$`. If it does not match, ask for a valid Hex package identifier inste...