fix(cli): isolate temporary config paths

[floze-the-genius]

Summary

Make the CLI test helper assign a unique path to every temporary config, even when parallel tests reuse the same descriptive name.

Motivation

TempConf previously keyed paths only by the caller-provided name and process ID. Reusing a name inside one test binary caused one instance to overwrite or delete another instance's file.

Closes #35.

Changes

• append a process-local atomic ID to each TempConf path
• add a regression covering two live configs with the same name and different contents

Compatibility Check

FerrumKV targets RESP2 / Redis semantics. If this change touches wire behaviour or command semantics:

• This matches Redis behaviour exactly.
• This is an intentional deviation — documented in README and asserted by a test, and tracked as a FERRUM-NNN issue.
• N/A (no wire/semantic change).

Quality Gates — all must pass before requesting review

cargo fmt --all -- --check
cargo clippy --all-targets --all-features -- -D warnings
cargo test --all-targets --all-features
cargo bench --no-run --all-features

• cargo fmt --check clean
• cargo clippy -- -D warnings clean
• cargo test green
• cargo bench --no-run compiles
• No new unsafe (or each block has a // SAFETY: justification)
• Binary safety preserved — no String/str in the data path
• Key-removal paths call track_remove + aof.append_del (if AOF)

Test Plan

• confirmed the regression fails on master because both same-name instances resolve to the same path
• cargo test temp_conf_paths_are_unique_for_reused_names -- --nocapture
• repeated the focused regression 100 times
• ran all four quality gates above

AI Assistance Disclosure

This pull request was implemented and validated with OpenAI Codex. The issue selection, repository policy checks, code changes, tests, and PR text were AI-assisted.

[phaethix]

Thanks for picking this up, @floze-the-genius! The atomic-id approach is exactly the fix the linked issue (#35) called for, and the added regression test is the right call. I verified it locally (fmt + clippy + full test suite all green) and will merge once CI passes. Appreciate the clean, well-scoped contribution.