Add editable git commit prompt to rule store

[0x524c]

Custom Git Commit Prompt Support

Adds user-customizable AI prompts for commit message generation via Rules Library integration.

Features

UI Integration:

• Rules Library: Settings → AI → Rules Library → “Git Commit Prompt” (built-in rule)
• Reset button (↻): Restores default prompt content with one click
• Title handling: Title is fixed to “Git Commit Prompt”; body remains fully editable
• Toggle behavior: Checkmark icon still controls whether the rule is active (metadata.default flag)

Functionality:

• Custom prompt storage: Reuses Zed’s Rules Library (LMDB/heed) database
• Activation control: Custom prompt only used when metadata.default = true
• Auto-fallback: Falls back to bundled default prompt whenever the rule is inactive or loading fails
• Rule lifecycle: Commit prompt is created with default content during initial database setup
• Default state: Enabled by default (default = true on first initialization)

Implementation

Key files touched:

• crates/prompt_store/src/prompt_store.rs – Adds PromptId::CommitMessage, initializes database entry, and forces the title to “Git Commit Prompt” when saving
• crates/rules_library/src/rules_library.rs – Allows body edits, keeps title read-only, exposes reset action, and omits deletion for the built-in rule
• crates/git_ui/src/git_panel.rs – Loads custom prompt only when metadata.default is true, otherwise uses the default text
• crates/agent/src/agent.rs / crates/agent_ui/src/context_picker/rules_context_picker.rs – Hide the CommitMessage rule from agent pickers
• crates/git_ui/Cargo.toml – Adds prompt_store dependency
• Housekeeping: legacy ad-hoc tests (git_commit_prompt_tests.rs / git_custom_commit_tests.rs) removed after migrating coverage

Key Implementation Details:

• PromptId enum gains a CommitMessage variant alongside EditWorkflow and User
• Special-cased store logic keeps the prompt editable but enforces the canonical title
• metadata.default flag (toggled from the Rules Library) governs activation during commit generation
• Reset action reinstates the default commit prompt content (and preserves the active/inactive flag)
• Database bootstrapping ensures the built-in rule exists with default content
• Git panel falls back gracefully to bundled text whenever the custom rule is inactive or fails to load

Testing:

• Targeted coverage via cargo test -p prompt_store -- git_commit_prompt
  • Initialization with default metadata and content
  • Custom body persistence while keeping title immutable
  • Default-flag persistence across sessions (drop/reopen LMDB)
  • Metadata cache refresh after saving custom content

Use Case:

Enables teams and individuals to enforce custom commit conventions (e.g., conventional commits, ticket references, specific format requirements) without modifying Zed source code.

Release Notes:

Feat: persist customizable git commit prompt

- register PromptId::CommitMessage as the built-in "Git Commit Prompt"
- seed PromptStore with commit_message_prompt.txt as the default body
- allow editing only the prompt body, keep the title immutable, and add reset support
- load the custom commit prompt in the git panel only when marked as default, otherwise fall back
- enforce the title invariant in PromptStore::save and refresh cached prompts after updates

[zed-industries-bot]

	Warnings
:warning:	This PR is missing release notes. Please add a "Release Notes" section that describes the change: Release Notes: - Added/Fixed/Improved ... If your change is not user-facing, you can use "N/A" for the entry: Release Notes: - N/A

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[0x524c]

https://github.com/user-attachments/assets/d5db0cf9-8d66-4cd4-a099-bb30434d6762

[0x524c]

There is still a layout issue: the "Git Commit Prompt" rule title still allows selection and cursor movement over it. In my opinion, this shouldn't be possible, but I haven't been able to fix it yet. Currently, it only doesn't allow editing and deletion.