Summary

Fixes #3592

Fix terminal TUI autocomplete so Enter submits when the currently selected completion item is already fully present in the
input token.

This fixes /resume 1 when both 1 and 10 remain in the completion list. Previously, Enter was captured by the
completion menu and kept accepting the already-inserted 1, so the command did not submit.

Changes

• Add completionSelectedInsertPresent() to detect when the selected completion insert already matches the current token.
• Let Enter close the completion menu and fall through to normal submission in that exact-match case.
• Add a regression test for /resume 1 with both 1 and 10 present.

Scope

This is limited to TUI autocomplete Enter handling. Tab behavior is unchanged.

The fix is intentionally generic for exact selected inserts, so it also avoids the same stuck-Enter behavior for other
completion menus where the selected item is already fully typed but other prefix matches remain.

Tests

• go test ./internal/cli -run 'TestSlashCompletion|TestSlashArgCompletion|TestEnterOnExactMCPSubmitsManager| TestEnterOnMCPWithTrailingSpaceSubmitsManager|TestEnterOnExactSlashArgSubmitsWhenPrefixAlsoMatches| TestCompletionClosesOnSpaceAndNonMatch|TestActiveAtToken|TestMoveCompletionWraps' -count=1
• go test ./internal/cli -count=1
• env GOCACHE=/private/tmp/reasonix-gocache go build -o /tmp/reasonix-test ./cmd/reasonix
• git diff --check