fix: execute config commands in declaration order (#39)

[codesoda]

Summary

• Replace BTreeMap<String, CommandDef> with IndexMap<String, CommandDef> so config commands execute in TOML declaration order instead of alphabetical key order
• Add indexmap dependency (already a transitive dep, zero new supply-chain cost)
• Add tests verifying declaration-order execution and TOML deserialization order
• Bump version to v0.4.1, update CHANGELOG

Closes #39

Test plan

• cargo check passes
• cargo test — all 207 tests pass, including 2 new order-verification tests
• cargo clippy clean
• cargo fmt clean

[codesoda]

[cadence]

Cadence PR Review

Goal
Fix issue #39 by making config-defined commands execute in the same order they appear in bugatti.config.toml, while preserving keyed lookup and updating tests and release metadata accordingly.

Signal	Details
Score	tight requirement match with solid verification
Models	claude-opus-4-6
Phases	20% planning, 70% implementation, 10% release/update work

Key Decisions

• The user chose the narrow fix proposed in the issue: replace BTreeMap with an order-preserving map rather than add naming conventions or compatibility shims.
• The model propagated the map-type change across config consumers and test helpers instead of localizing it only at the execution site.
• The user and model treated this as a patch release, updating version and changelog alongside the behavioral fix.

Outcome

The model appears to have met the stated goal cleanly: command iteration now follows declaration order, and the PR includes targeted tests plus the expected release bookkeeping. There is no meaningful evidence of drift or overreach beyond the intentional type substitution needed to carry the behavior through the codebase.

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