chore(beads): migrate issue tracking from bd to br

Agents were told to run bd commands that beads_rust does not have (bd prime,
bd remember, bd dolt push, bd tag, bd note, bd children), and bd's git hooks
were still active, so bd could re-export its stale dolt state over br's
JSONL on commit.

- Rewrite AGENTS.md, docs/agents/issue-tracker.md, docs/agents/triage-labels.md
  and the .serena memories around br's real CLI surface
- Replace bd's generated AGENTS.md block with br's (br agents --add)
- Point the .claude session hooks at `br robot-docs guide`
- Remove bd git hooks and unset core.hooksPath; br installs no hooks
- Ignore br runtime files (local SQLite DB, recovery and merge artifacts)
- Rewrite .beads/README.md, config.yaml and metadata.json for br

Issue: nix-overlay-6pp

.beads/config.yaml

@@ -1,56 +1,8 @@
-# Beads Configuration File
-# This file configures default behavior for all bd commands in this repository
-# All settings can also be set via environment variables (BD_* prefix)
-# or overridden with command-line flags
+# Beads Project Configuration
+# issue_prefix: nix-overlay
+# default_priority: 2
+# default_type: task
 
-# Issue prefix for this repository (used by bd init)
-# If not set, bd init will auto-detect from directory name
-# Example: issue-prefix: "myproject" creates issues like "myproject-1", "myproject-2", etc.
-# issue-prefix: ""
-
-# Use no-db mode: JSONL-only, no Dolt database
-# When true, bd will use .beads/issues.jsonl as the source of truth
-# no-db: false
-
-# Enable JSON output by default
-# json: false
-
-# Feedback title formatting for mutating commands (create/update/close/dep/edit)
-# 0 = hide titles, N > 0 = truncate to N characters
-# output:
-#   title-length: 255
-
-# Default actor for audit trails (overridden by BEADS_ACTOR or --actor)
-# actor: ""
-
-# Export events (audit trail) to .beads/events.jsonl on each flush/sync
-# When enabled, new events are appended incrementally using a high-water mark.
-# Use 'bd export --events' to trigger manually regardless of this setting.
-# events-export: false
-
-# Multi-repo configuration (experimental - bd-307)
-# Allows hydrating from multiple repositories and routing writes to the correct database
-# repos:
-#   primary: "."  # Primary repo (where this database lives)
-#   additional:   # Additional repos to hydrate from (read-only)
-#     - ~/beads-planning  # Personal planning repo
-#     - ~/work-planning   # Work planning repo
-
-# JSONL backup (periodic export for off-machine recovery)
-# Auto-enabled when a git remote exists. Override explicitly:
-# backup:
-#   enabled: false     # Disable auto-backup entirely
-#   interval: 15m      # Minimum time between auto-exports
-#   git-push: false    # Disable git push (export locally only)
-#   git-repo: ""       # Separate git repo for backups (default: project repo)
-
-# Integration settings (access with 'bd config get/set')
-# These are stored in the database, not in this file:
-# - jira.url
-# - jira.project
-# - linear.url
-# - linear.api-key
-# - github.org
-# - github.repo
-
-sync.remote: "git+ssh://git@git.millerson.name:22002/alex/millerson-overlay.nix.git"
+# Remote for beads state. The JSONL export in .beads/issues.jsonl is committed
+# to git, so `git push` is what carries issue state to the shared repository.
+sync.remote: "git+ssh://git@git.millerson.name:22002/alex/millerson-overlay.nix.git"