docs: add missing v1.2.20 features documentation (#23086)

## Summary
- Document automatic yarn.lock migration in lockfile docs
- Add --recursive flag documentation for bun outdated/update commands  
- Document Windows long path support in installation docs

## Test plan
Documentation only - no code changes to test.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>

docs/cli/update.md

@@ -90,6 +90,17 @@ Packages are organized in sections by dependency type:
 
 Within each section, individual packages may have additional suffixes (` dev`, ` peer`, ` optional`) for extra clarity.
 
+## `--recursive`
+
+Use the `--recursive` flag with `--interactive` to update dependencies across all workspaces in a monorepo:
+
+```sh
+$ bun update --interactive --recursive
+$ bun update -i -r
+```
+
+This displays an additional "Workspace" column showing which workspace each dependency belongs to.
+
 ## `--latest`
 
 By default, `bun update` will update to the latest version of a dependency that satisfies the version range specified in your `package.json`.

docs/install/lockfile.md

@@ -46,3 +46,13 @@ print = "yarn"
 Bun v1.2 changed the default lockfile format to the text-based `bun.lock`. Existing binary `bun.lockb` lockfiles can be migrated to the new format by running `bun install --save-text-lockfile --frozen-lockfile --lockfile-only` and deleting `bun.lockb`.
 
 More information about the new lockfile format can be found on [our blogpost](https://bun.com/blog/bun-lock-text-lockfile).
+
+#### Automatic lockfile migration
+
+When running `bun install` in a project without a `bun.lock`, Bun automatically migrates existing lockfiles:
+
+- `yarn.lock` (v1)
+- `package-lock.json` (npm)
+- `pnpm-lock.yaml` (pnpm)
+
+The original lockfile is preserved and can be removed manually after verification.