fix(modifiers): fail closed when modifiers-napi is the public stub

[xjdr-noumena]

Summary

modifiers-napi@0.0.1 on public npm is a reservation stub with no exports. isModifierPressed previously destructured isModifierPressed from require('modifiers-napi') and called it unconditionally — when the stub resolves, the function is undefined and the call throws TypeError: nativeIsModifierPressed is not a function on every Enter keystroke.

The only call site (src/hooks/useTextInput.ts:263 in handleEnter) is gated on env.terminal === 'Apple_Terminal' as a workaround for Apple Terminal not supporting custom Shift+Enter keybindings. The throw bubbles up through the Ink input dispatch and blocks the Enter submit pipeline, so Terminal.app users cannot submit prompts interactively. Every other terminal (iTerm2, Ghostty, Kitty, VSCode) takes a different branch and is unaffected.

Fix

Guard the destructure. If the export is not a function, fail closed: report the modifier as not pressed. This disables best-effort Shift+Enter newline detection on Apple Terminal (a nicety) while restoring Enter submit. Returning false is the safe fallback — the path only ever asked whether Shift was held.

prewarmModifiers is already wrapped in try/catch and is unaffected.

Tests

src/utils/modifiers.test.ts adds two cases:

• darwin + stub-shape (no isModifierPressed export): returns false instead of throwing. This is the exact regression that blocked Enter on Apple Terminal.
• non-darwin: returns false without ever consulting the stub.

Verified locally: bun test src/utils/modifiers.test.ts → 2 pass, 0 fail. Package smoke (bun run test:package-smoke) builds clean on this branch.

What this doesn't claim

• I did not run an end-to-end Enter-submit test under real TERM_PROGRAM=Apple_Terminal — that requires macOS Terminal.app. The unit test proves the guard path runs and returns false rather than throwing the TypeError; reporter (@RasputinKaiser) can verify the interactive Enter submit.

Closes #44.

Follow-up

The deeper pattern — modifiers-napi being a reservation stub in the OSS dependency tree — is the same class of stub problem tracked in #42 (native image processor). A real modifiers-napi N-API binding to CGEventSourceFlagsState would close the gap permanently and re-enable the Apple Terminal Shift+Enter newline detection. That belongs with #42, not this fix.

[RasputinKaiser]

It's working for me

[RasputinKaiser]

It works locally for me