feat(ai-commit-msg): support XDG_CONFIG_HOME config files

[stephansama]

Closes STE-39

Extends cosmiconfig searchPlaces in core/ai-commit-msg/src/config.ts to include XDG base-directory paths ($XDG_CONFIG_HOME/ai-commit-msg/config.{json,yaml,yml,toml}, fallback $HOME/.config/ai-commit-msg/). Adds a smol-toml cosmiconfig loader so .toml configs at the XDG path round-trip correctly. Project-local config files still take precedence over XDG-sourced ones.

Acceptance criteria

• A config at ~/.config/ai-commit-msg/config.json is discovered and loaded
• A config at $XDG_CONFIG_HOME/ai-commit-msg/config.yaml is discovered when XDG_CONFIG_HOME is set
• TOML config files at the XDG path are parsed correctly
• Local project config still takes precedence over XDG config
• No regression in existing cosmiconfig search behaviour

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Project	Deployment	Actions	Updated (UTC)
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• core/ai-commit-msg/package.json
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[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
251	1	250	0

View the top 1 failed test(s) by shortest run time

core/ai-commit-msg/test/config.test.ts > test/config.test.ts

Stack Traces | 0s run time

Error: [vitest] No "defaultLoaders" export is defined on the "cosmiconfig" mock. Did you forget to return it from "vi.mock"?
If you need to partially mock a module, you can use "importOriginal" helper inside:

vi.mock(import("cosmiconfig"), async (importOriginal) => {
  const actual = await importOriginal()
  return {
    ...actual,
    // your mocked methods
  }
})

 ❯ src/config.ts:20:5
 ❯ test/config.test.ts:6:1

To view more test analytics, go to the Test Analytics Dashboard
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[gemini-code-assist]

Code Review

This pull request adds support for TOML configuration files and XDG-compliant global configuration paths using smol-toml and xdg-app-paths. The review identifies a critical issue where including absolute XDG paths in the cosmiconfig search list disrupts the configuration hierarchy, potentially allowing global settings to override local ones. Further improvements are suggested regarding the use of standard XDG file naming conventions and extending TOML support to project-local configuration files for better consistency.

[gemini-code-assist]

Including absolute paths in searchPlaces breaks the configuration hierarchy. cosmiconfig searches all searchPlaces for every directory it traverses upwards. Because these XDG paths are absolute, they will be matched during the search of the current working directory, effectively overriding any project-local configuration files located in parent directories (e.g., a .ai-commit-msgrc in the project root would be ignored if a global XDG config exists).

To correctly implement a global fallback while maintaining the expected priority (local > parent > global), you should remove these absolute paths from searchPlaces and instead attempt to load them manually in loadConfig only if explorer.search() returns null.

[gemini-code-assist]

These search places use a "double-hidden" pattern (a hidden file inside a hidden directory, e.g., .config/.ai-commit-msgrc). This is unconventional for XDG-style configuration. Standard practice is to use non-hidden filenames within the .config directory (e.g., .config/ai-commit-msgrc), which cosmiconfig's getDefaultSearchPlaces already covers. If the intention was to support a dedicated subdirectory, a pattern like .config/${moduleName}/config.json would be more standard.

[gemini-code-assist]

The TOML loader is currently only utilized for the XDG configuration path. For consistency and to support users who prefer TOML for project-specific settings, you should also add TOML variants to the project-local search places (e.g., .${moduleName}rc.toml and .config/${moduleName}rc.toml).

`${xdgConfigDirectory}.toml`,
		`.${moduleName}rc.toml`,
		`.config/${moduleName}rc.toml`,