fix(chisel): clean up stale session cache file on rename

[Osraka]

Closes #15796

What

When a saved Chisel session is saved again under a different ID, the new cache file is written but the old chisel-<id>.json file remains. This makes !list show a stale session and allows the old ID to be loaded.

This change removes the previous cache file after the renamed session is successfully written. Re-saving with the same ID is unchanged, and a missing old file is treated as a no-op.

Tests

• Added a REPL regression test covering !save with two IDs, !list, !load <old-id>, and !load latest.
• cargo test -p chisel --test it -- save_renamed_session_removes_stale_cache -- --exact
• cargo test -p chisel
• cargo fmt --all --check
• git diff --check

The full package test was also run with network access for the Solc/Foundry fixtures.

[mablr]

The rename behavior makes sense and the normal write-before-delete flow is correct, but the case-insensitive path collision and use of the real user cache in the regression test should be fixed before merge. Also, the documented focused command needs the module-qualified test name: repl::save_renamed_session_removes_stale_cache; as written, it runs 0 tests.

[Osraka]

Addressed the review feedback in commit fd16fa0.

• Compare the canonical old and newly written cache paths before removing the old ID, preserving the destination for case-only renames on case-insensitive filesystems.
• Use collision-resistant cache IDs with Drop cleanup in the REPL regression tests.
• Assert the new cache filename from !list via sendln_raw and load the new ID explicitly.

Validation:

• cargo test -p chisel --lib (11 passed)
• cargo fmt --all -- --check
• git diff --check

The focused REPL integration test currently times out before the prompt in this macOS environment, before the rename scenario runs; the library suite and production binary compilation pass.

[Osraka]

Follow-up for the CI failure: the clippy job reported clippy::redundant-clone at crates/chisel/src/dispatcher.rs:295.

Fixed in commit 0fca37f by moving previous_id into the diverging write-error branch instead of cloning it. The maintainer merge commit was preserved before pushing this fix.

Validation:

• cargo test -p chisel --test it repl::save_ -- --nocapture: 2 passed
• cargo test -p chisel --test it repl::failed_save_restores_previous_session_id -- --exact --nocapture: 1 passed
• cargo test -p chisel --lib: 11 passed
• cargo fmt --all -- --check
• git diff --check

The local toolchains do not have the clippy component installed, so the repository CI is the clippy verification for this one-line lint fix.

[mablr]

This failure fixture still depends on state in the real user cache: if ~/.foundry/cache/chisel/chisel-invalid/ already exists, this save succeeds instead of exercising rollback. Please build the missing parent from unique_cache_id (for example, <unique-id>/id) and assert the save error before consuming the prompt.

[mablr]

On a case-sensitive filesystem this only proves that the destination survives; it does not prove that the old lowercase cache was removed. An implementation that skips every case-only cleanup would pass while leaving both files. Please detect whether the two paths alias and, when they are distinct, also assert that loading old_id fails.

[Osraka]

Addressed both follow-ups in d2aa655.

• The failed-save fixture now uses a per-test missing parent (<unique-id>/id) and asserts the write error before consuming the prompt.
• The case-only rename test now detects whether the two cache paths alias; when they are distinct, it also verifies that loading old_id fails.

Validation:

• cargo test -p chisel --test it repl::save_case_only_rename_preserves_destination
• cargo test -p chisel --test it repl::save_renamed_session_removes_stale_cache
• cargo test -p chisel --test it repl::failed_save_restores_previous_session_id
• cargo test -p chisel --lib
• cargo +nightly fmt -p chisel --check
• git diff --check