Reduce redundant state writes and streamline tests and docs

[jiminu]

Repeated configuration installs rewrote identical managed state, and the test runner waited for each full batch before scheduling more suites. Skip byte-identical state writes while preserving atomic updates, and refill available test workers while retaining ordered logs and failure reporting.

Also recognize tracked mise configurations by file identity so symlinked paths and repeated separators do not prevent safe pruning. Consolidate redundant tests and comments, and simplify README and maintenance documentation while preserving lifecycle safeguards.

Validation:

• bash scripts/check.sh: passed locally on macOS, including all 21 test suites, syntax, ShellCheck, and formatting checks.
• Regression coverage verifies unchanged state files, required pending-state writes, aliased mise paths, worker scheduling, and failure reporting. Code review completed; identified failure-count issue fixed and rechecked.
• Isolated local measurements: repeated configuration install median 424 → 330 ms across 12 alternating samples per version; full suite 44.0 → 37.3 seconds in one comparison. Results are machine-specific; shell startup behavior is unchanged.
• Markdown local links and code fences checked; git diff --check passed.