[FEATURE] Add TOML linting as a pre-commit hook

[c-vigo]

Summary

Add TOML linting to the pre-commit pipeline so TOML files are validated consistently in local development and CI.

Problem / Motivation

TOML files currently lack dedicated lint enforcement, which can allow format or style drift and late CI failures.

Proposed Solution

Wire a TOML linter as a pre-commit hook, pinned to a stable version, and run it on TOML files in this repository.

Acceptance Criteria

• TOML linting hook is added to .pre-commit-config.yaml with a pinned version
• Repository TOML files pass the new lint check
• uv run pre-commit run --all-files passes with the hook enabled
• CI runs the same TOML lint check without extra manual setup
• TDD compliance (see .cursor/rules/tdd.mdc)

Out of Scope

• Non-TOML linting changes
• Broad pre-commit refactors unrelated to TOML

Related Issues

Related to #122
Related to #161

Priority

Medium

Changelog Category

Added

Additional Context

Goal: TOML linting as a pre-commit hook.

[c-vigo]

Implementation plan for #181 (no claim, no code changes yet)

Chosen TOML tool: Taplo (ComPWA/taplo-pre-commit), pinned to a stable revision.
Reason: mature + widely adopted TOML toolkit with reliable pre-commit integration; complements existing check-toml syntax validation.

Plan:

1. Update root .pre-commit-config.yaml
   • Keep existing check-toml hook
   • Add pinned Taplo hook (taplo-lint)
2. Mirror the same hook update in assets/workspace/.pre-commit-config.yaml to keep workspace template parity.
3. Verify locally:
   • uv run pre-commit run --all-files
4. Confirm CI parity:
   • No workflow changes expected, since CI already runs uv run pre-commit run --all-files via .github/actions/test-project/action.yml.
5. Validate acceptance criteria and include evidence in the PR notes.

Scope guardrails:

• In scope: TOML linting hook addition only
• Out of scope: unrelated pre-commit refactors and non-TOML linting changes