feat: add context optimization features for AI agents (#297)

* feat: add bd prime and setup commands for AI agent integration

This commit consolidates context optimization features for AI agents:

## New Commands

**bd prime** - AI-optimized workflow context injection
- Outputs ~1-2k tokens of workflow context
- Context-aware: adapts to MCP vs CLI mode
- MCP mode: minimal reminders (~500 tokens)
- CLI mode: full command reference (~1-2k tokens)
- Warns against TodoWrite tool and markdown TODOs
- Designed for SessionStart/PreCompact hooks

**bd setup claude** - Claude Code integration installer
- Installs hooks via JSON configuration (not file scripts)
- Supports --project for project-only installation
- Supports --check to verify installation
- Supports --remove to uninstall hooks
- Idempotent (safe to run multiple times)
- Merges with existing settings

**bd setup cursor** - Cursor IDE integration installer
- Creates .cursor/rules/beads.mdc with workflow rules
- Simplified implementation (just overwrites file)

## bd doctor Enhancements

- New: CheckClaude() verifies Claude Code integration
- Detects plugin, MCP server, and hooks installation
- Provides actionable fix suggestions
- Extracted legacy pattern detection to doctor/legacy.go
- Detects JSONL-only mode and warns about legacy issues.jsonl

## Core Improvements

- FindBeadsDir() utility for cross-platform .beads/ discovery
- Works in JSONL-only mode (no database required)
- Sorted noDbCommands alphabetically (one per line for easy diffs)

## Testing

- Unit tests for setup command hook manipulation
- Tests for idempotency, adding/removing hooks
- All tests passing

## Documentation

- cmd/bd/doctor/claude.md - Documents why beads doesn't use Claude Skills
- commands/prime.md - Slash command for bd prime
- Fixed G304 gosec warnings with nosec comments

## Token Efficiency

The bd prime approach reduces AI context usage dramatically:
- MCP mode: ~500 tokens (vs ~10.5k for full MCP tool scan)
- CLI mode: ~1-2k tokens
- 80-99% reduction in standing context overhead

* fix: resolve linting errors in setup utils and remove obsolete test

- Add error check for tmpFile.Close() in setup/utils.go to fix golangci-lint G104
- Remove TestCheckMultipleJSONLFiles test that referenced deleted checkMultipleJSONLFiles function

Fixes golangci-lint errcheck violations introduced in the bd prime/setup feature.

cmd/bd/main.go

@@ -142,7 +142,22 @@ var rootCmd = &cobra.Command{
 		}
 
 		// Skip database initialization for commands that don't need a database
-		noDbCommands := []string{"init", cmdDaemon, "help", "version", "quickstart", "doctor", "merge", "completion", "bash", "zsh", "fish", "powershell"}
+		noDbCommands := []string{
+			cmdDaemon,
+			"bash",
+			"completion",
+			"doctor",
+			"fish",
+			"help",
+			"init",
+			"merge",
+			"powershell",
+			"prime",
+			"quickstart",
+			"setup",
+			"version",
+			"zsh",
+		}
 		if slices.Contains(noDbCommands, cmd.Name()) {
 			return
 		}