test: cover dotenv parse, remove, and append helpers

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Summary

Adds Vitest coverage for src/lib/dotenv-parse.ts, which backs .env handling in the vault file workspace and tRPC secrets parsing.

Risky behavior now covered

• parseDotenv: comment/blank skipping, trimming, first = semantics, quoted values, CRLF.
• removeDotenvKey: removes lines that parse as the target key while preserving comments and blank structure.
• appendDotenvKey: validation (empty key, = in key, # prefix, newlines in key/value), duplicate key detection, when values are quoted vs unquoted, escaping of " and \ inside quoted strings, trimming trailing whitespace before append.

Test files

• Added: src/lib/dotenv-parse.test.ts

Why this reduces regression risk

This module encodes parsing and serialization rules for secrets stored as dotenv text. A mistake here can corrupt files, leak malformed lines, or allow invalid keys—high blast radius across UI and API. These tests pin the contract without snapshots or environment coupling.

Validation

• npm run test (Vitest) — all tests pass; deterministic node environment.