Add beads issue tracking infrastructure

Initialize beads (br) for dependency-aware issue tracking in this project.
Beads provides a lightweight task database with graph-aware triage, used
for coordinating work on the JSONL-first discovery feature.

Files added:
- .beads/config.yaml: Project configuration (issue prefix, defaults)
- .beads/issues.jsonl: Issue database with JSONL-first discovery tasks
- .beads/metadata.json: Beads metadata (commit correlation, etc.)
- .beads/.gitignore: Ignore SQLite databases, lock files, temp files

Also ignore .bv/ (beads viewer local state) in project .gitignore.

Beads is non-invasive: it never executes git/jj commands. The .beads/
directory is manually committed alongside code changes.

Usage:
- br ready --json: Find unblocked work
- br update <id> --status in_progress: Claim a task
- br close <id> --reason "done": Complete a task
- bv --robot-triage: Get graph-aware recommendations

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.beads/config.yaml

@@ -0,0 +1,4 @@
+# Beads Project Configuration
+# issue_prefix: bd
+# default_priority: 2
+# default_type: task