fix(ai): prevent async suggestion duplication

- Add buffer validation to check suggestion starts with buffer
- Discard stale suggestions that don't match current content

Fixes text duplication bug when accepting async suggestions after
buffer changes during suggestion fetch.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.claude/git.local.md

@@ -0,0 +1,52 @@
+---
+enabled: true
+# Commit Message Conventions
+scopes:
+  - ai
+  - widget
+  - strategy
+  - spec
+  - integration
+  - option
+  - docs
+  - ci
+types:
+  - feat
+  - fix
+  - docs
+  - refactor
+  - test
+  - chore
+  - perf
+  - style
+# Branch Naming Conventions
+branch_prefixes:
+  feature: feature/*
+  fix: fix/*
+  hotfix: hotfix/*
+  refactor: refactor/*
+  docs: docs/*
+# .gitignore Generation Defaults
+gitignore:
+  os: [macos, linux, windows]
+  languages: [ruby, shell]
+  frameworks: []
+  tools: [rspec, github-actions]
+---
+
+# Project-Specific Git Settings
+
+This file configures the `@git/` plugin for this project. The settings above in the YAML frontmatter define valid scopes, types, and branch naming conventions that the plugin will enforce.
+
+## Usage
+
+- **Scopes**: When creating a commit with `/commit`, choose from the defined `scopes`.
+- **Branching**: When creating a new branch via the `git` skill, use the defined `branch_prefixes`.
+- **Gitignore**: When running `/gitignore` without arguments, the technologies listed above will be used as defaults.
+
+## Additional Guidelines
+
+- Always run tests before committing.
+- Ensure linting passes before pushing.
+- Reference issue numbers in commit footers (e.g., `Closes #123`).
+- Use `BREAKING CHANGE:` prefix in the body for breaking changes.