feat: support reading bun version from mise.toml

[leetrout]

Summary

• Add mise.toml and .mise.toml to the supported version file readers
• Use the existing @iarna/toml dependency for robust TOML parsing (handles both string and array formats under [tools])
• Update README to document mise.toml as a bun-version-file option

Fixes #184

🤖 Generated with Claude Code

[coderabbitai]

Walkthrough

This PR adds support for reading Bun versions from mise.toml configuration files. It introduces TOML parsing, implements a new reader function to extract the tools.bun field from mise configuration, integrates it into the existing version-file lookup system, and updates documentation.

Changes

Mise version file support

Layer / File(s)	Summary
TOML parser and mise reader implementation src/utils.ts	Import TOML parser from @iarna/toml and implement readMiseToml() function to parse mise.toml content and extract the tools.bun field, handling both string and array configurations.
Reader integration and documentation src/utils.ts, README.md	Wire the new mise reader into FILE_VERSION_READERS for both mise.toml and .mise.toml filenames, and update README to document these new supported version-file names.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The pull request title accurately summarizes the main change: adding support for reading bun version from mise.toml files.
Description check	✅ Passed	The pull request description clearly relates to the changeset, providing a summary of changes made and linking to the relevant issue #184.
Linked Issues check	✅ Passed	The pull request meets the requirement from issue #184 by implementing support for reading bun version from mise.toml and .mise.toml files.
Out of Scope Changes check	✅ Passed	All changes are directly related to the scope of issue #184: adding mise.toml support, updating README documentation, and implementing TOML parsing.

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@README.md`:
- Line 84: Update the README entry for `bun-version-file` to document that both
`mise.toml` and `.mise.toml` are supported: modify the table cell listing
example files to include `.mise.toml` (e.g., change "package.json, mise.toml" to
"package.json, mise.toml, .mise.toml"), and add a short note referencing
FILE_VERSION_READERS support if present so users know the hidden filename is
intentional.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: c7e628cd-984d-48d6-97e3-49745bad5011

📥 Commits

Reviewing files that changed from the base of the PR and between 0c5077e and 5bb1c1b.

⛔ Files ignored due to path filters (2)

• dist/cache-save/index.js is excluded by !**/dist/**
• dist/setup/index.js is excluded by !**/dist/**

📒 Files selected for processing (2)

• README.md
• src/utils.ts

[coderabbitai]

⚠️ Potential issue | 🟡 Minor | ⚡ Quick win

Document .mise.toml alongside mise.toml.

FILE_VERSION_READERS now supports both mise.toml and .mise.toml, but the input docs only mention the non-hidden filename. That leaves the new supported variant effectively undocumented for users.

Suggested doc tweak

-| `bun-version-file` | The version of Bun to download and install from file.                             | `undefined`                              | `package.json`, `.bun-version`, `.tool-versions`, `mise.toml` |
+| `bun-version-file` | The version of Bun to download and install from file.                             | `undefined`                              | `package.json`, `.bun-version`, `.tool-versions`, `mise.toml`, `.mise.toml` |

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

	| `bun-version-file` | The version of Bun to download and install from file. | `undefined` | `package.json`, `.bun-version`, `.tool-versions`, `mise.toml` |
	| `bun-version-file` | The version of Bun to download and install from file. | `undefined` | `package.json`, `.bun-version`, `.tool-versions`, `mise.toml`, `.mise.toml` |

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@README.md` at line 84, Update the README entry for `bun-version-file` to
document that both `mise.toml` and `.mise.toml` are supported: modify the table
cell listing example files to include `.mise.toml` (e.g., change "package.json,
mise.toml" to "package.json, mise.toml, .mise.toml"), and add a short note
referencing FILE_VERSION_READERS support if present so users know the hidden
filename is intentional.