Fix #264 and #262: Remove stale --resolve-collisions references

- Update examples/git-hooks README to use 'bd hooks install' instead of non-existent install.sh
- Fix post-merge hook error message to not suggest --resolve-collisions flag (removed in v0.20)
- Clean up all doc references to --resolve-collisions (flag removed, hash IDs prevent collisions)

Fixes #264 (git hooks installer missing)
Fixes #262 (misleading error message)

Amp-Thread-ID: https://ampcode.com/threads/T-c9f0e4cb-fba2-4db2-a3d5-36dc1892be9d
Co-authored-by: Amp <amp@ampcode.com>

examples/git-hooks/README.md

@@ -30,13 +30,13 @@ These git hooks ensure bd changes are always synchronized with your commits and
 
 ### Quick Install (Recommended)
 
-From your repository root:
+Use `bd hooks install` to install hooks automatically:
 
 ```bash
-./examples/git-hooks/install.sh
+bd hooks install
 ```
 
-Or use `bd init --quiet` to install hooks automatically.
+Alternatively, use `bd init --quiet` which installs hooks during initialization.
 
 **Hook Chaining (New in v0.23):** If you already have git hooks installed (e.g., pre-commit framework), bd will:
 - Detect existing hooks