docs: CONTRIBUTING.md + issue templates — the musician contribution path (task H-02)

'Add a style without deep coding' centerpiece: KB data contract, mirror gospel pack,
register, run validator; explains why the validator exists; /kb-expand assisted path;
PR checklist. add-style/bug_report/feature_request templates + config.yml. License flagged
unsettled, not decided. Critic PASS (all links/commands verified, schema-faithful).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,31 @@
+---
+name: Bug report
+about: Something isn't working as expected
+title: "[Bug] "
+labels: ["bug"]
+---
+
+## What happened?
+
+<!-- A clear, short description of the bug. -->
+
+## Steps to reproduce
+
+1.
+2.
+3.
+
+## What you expected instead
+
+
+
+## Environment
+
+- OS:
+- How you ran it: <!-- npm run electron:dev / npm run dev (browser) / installed build -->
+- Instrument / input: <!-- e.g. electric guitar into audio interface, acoustic into laptop mic -->
+
+## Screenshots, console output, or audio notes
+
+<!-- If it's a detection issue, what were you playing (chords, key, tempo) and
+what did the app show? -->