Merge PR #149: Add --no-db mode for JSONL-only operation

Implements --no-db mode to avoid SQLite corruption in multi-process scenarios.

Changes:
- Add in-memory storage backend (internal/storage/memory/)
- Add JSONL persistence layer (cmd/bd/nodb.go)
- Integrate --no-db flag into command flow
- Support config.yaml for no-db and issue-prefix settings
- Refactor atomic JSONL writes into shared helper

Co-authored-by: rrnewton <rrnewton@users.noreply.github.com>
Amp-Thread-ID: https://ampcode.com/threads/T-67d6d80f-27dc-490a-a95d-61ad06d5b06d
Co-authored-by: Amp <amp@ampcode.com>

.beads/config.yaml

@@ -0,0 +1,47 @@
+# 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
+
+# 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: load from JSONL, no SQLite, write back after each command
+# When true, bd will use .beads/issues.jsonl as the source of truth
+# instead of SQLite database
+no-db: false
+
+# Disable daemon for RPC communication (forces direct database access)
+# no-daemon: false
+
+# Disable auto-flush of database to JSONL after mutations
+# no-auto-flush: false
+
+# Disable auto-import from JSONL when it's newer than database
+# no-auto-import: false
+
+# Enable JSON output by default
+# json: false
+
+# Default actor for audit trails (overridden by BD_ACTOR or --actor)
+# actor: ""
+
+# Path to database (overridden by BEADS_DB or --db)
+# db: ""
+
+# Auto-start daemon if not running (can also use BEADS_AUTO_START_DAEMON)
+# auto-start-daemon: true
+
+# Debounce interval for auto-flush (can also use BEADS_FLUSH_DEBOUNCE)
+# flush-debounce: "5s"
+
+# 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