/feedback opens the Kigi GitHub issues page

Feedback about an unofficial community build belongs on its own issue
tracker, not Moonshot's feedback endpoint — and this mirrors the
official kimi-cli, whose /feedback opens its repo's issues page
(ISSUE_URL in ui/shell/slash.py). /feedback now returns
Action::OpenUrl(https://github.com/ZacharyZhang-NY/Kigi-CLI/issues),
the same battle-tested browser path /docs web uses.

The now-dead TUI text-feedback pipeline is excised: PromptInputMode::
Feedback (~ prefix composer mode), Action::{EnterFeedbackMode,
SendFeedback}, Effect::SendFeedback (the kigi/feedback ACP POST),
TaskResult::{FeedbackComplete,FeedbackFailed}, and their dispatchers.
The shell-side kigi/feedback ACP extension stays: it is protocol
surface for editor embeddings, OAuth-gated, and shared with kigi/btw.

Gates: workspace check/clippy --all-targets 0/0, fmt, kigi-tui lib
6621 passed / 0 failed.

crates/codegen/kigi-tui/src/app/dispatch/tests/router.rs

@@ -32,23 +32,6 @@ fn seed_foreign_resume_hint(
         }),
     );
 }
-/// Sending feedback is a submit: it retires the active ephemeral tip.
-#[test]
-fn send_feedback_clears_active_ephemeral_tip() {
-    let mut app = test_app_with_agent();
-    let id = AgentId(0);
-    let agent = app.agents.get_mut(&id).unwrap();
-    let _ = agent.ephemeral_tip.show(
-        crate::tips::EphemeralTip::new("t", ratatui::text::Line::from("hint")),
-        &mut std::collections::HashMap::new(),
-    );
-    assert!(agent.ephemeral_tip.is_active());
-    let _ = dispatch(Action::SendFeedback("it broke".into()), &mut app);
-    assert!(
-        !app.agents.get(&id).unwrap().ephemeral_tip.is_active(),
-        "feedback submit must clear the tip"
-    );
-}
 /// Sending a remember note is a submit: it retires the active ephemeral tip.
 #[test]
 fn send_remember_note_clears_active_ephemeral_tip() {