The custom crossterm editor now supports prompt history, slash-command tab
completion, multiline editing, and Ctrl-C semantics that clear partial input
without always terminating the session. The live REPL loop now distinguishes
buffer cancellation from clean exit, persists session state on meaningful
boundaries, and renders tool activity in a more structured way for terminal
use.
Constraint: Keep the active REPL on the existing crossterm path without adding a line-editor dependency
Rejected: Swap to rustyline or reedline | broader integration risk than this polish pass justifies
Confidence: medium
Scope-risk: moderate
Reversibility: clean
Directive: Keep editor state logic generic in input.rs and leave REPL policy decisions in main.rs
Tested: cargo fmt --manifest-path rust/Cargo.toml --all; cargo clippy --manifest-path rust/Cargo.toml --all-targets --all-features -- -D warnings; cargo test --manifest-path rust/Cargo.toml
Not-tested: Interactive manual terminal smoke test for arrow keys/tab/Ctrl-C in a live TTY
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