feat(bun): add bun pm

[Ffinnis]

Summary

Adds bun/bunx package manager support across all JS tooling commands. Projects with bun.lockb/bun.lock now automatically use bunx instead of npx for tsc, next, prettier, playwright, prisma, vitest, and lint.

• detect_package_manager(): detects bun.lockb/bun.lock (highest priority)
• package_manager_exec(): routes through bunx for bun projects
• tsc, next, prisma: replaced hardcoded npx fallback with package_manager_exec()
• playwright: added "bun" branch alongside pnpm/yarn/npm
• strip_pm_prefix: recognizes bun prefix in lint args
• Discover rules: bun/bunx patterns, rewrite prefixes for all JS tools
• Error messages updated to mention bun as install option

Changes

• src/utils.rs: bun detection in detect_package_manager(), bunx in package_manager_exec()
• src/tsc_cmd.rs: use package_manager_exec("tsc") instead of hardcoded npx
• src/next_cmd.rs: use package_manager_exec("next") instead of hardcoded npx
• src/prisma_cmd.rs: create_prisma_command() delegates to package_manager_exec()
• src/main.rs: prisma passthrough via package_manager_exec() instead of npx
• src/playwright_cmd.rs: added bun branch to PM match
• src/lint_cmd.rs: added "bun" to strip_pm_prefix
• src/discover/rules.rs: 2 new patterns (bun, bunx), 2 new rules, bunx prefixes in all tool rules
• src/discover/registry.rs: 19 new tests for classify/rewrite
• src/format_cmd.rs, src/prettier_cmd.rs: error messages mention bun

Test plan

• cargo fmt --all --check && cargo clippy --all-targets && cargo test passes
• 19 new bun/bunx tests (classify, rewrite, strip_pm_prefix)
• PATTERNS/RULES alignment test passes (pre-existing)
• 728 total tests, 0 failures