feat(#3845): add J/K keyboard shortcuts for previous/next session navigation

Global j/k keydown bindings navigate the session list (j=next, k=prev), guarded
by _isInteractiveSwipeTarget so they never fire while typing in the composer or
any input/textarea/contenteditable. Modifier-key combos are ignored.

Closes #3845.

Co-authored-by: Rod Boev <rod.boev@gmail.com>

static/sessions.js

@@ -6169,3 +6169,22 @@ async function _confirmDeleteProject(proj){
 document.addEventListener('keydown',(e)=>{
   if(e.key==='Escape'&&_sessionSelectMode) exitSessionSelectMode();
 });
+
+// Keyboard session navigation — J/K bindings
+function navigateSession(dir){
+  const rows=[...document.querySelectorAll('.session-item[data-sid]')];
+  const sids=rows.map(r=>r.dataset.sid);
+  const cur=S.session&&S.session.session_id;
+  const i=sids.indexOf(cur);
+  if(i<0||!sids.length)return;
+  const next=sids[Math.min(Math.max(i+dir,0),sids.length-1)];
+  if(next&&next!==cur) loadSession(next);
+}
+
+document.addEventListener('keydown',(e)=>{
+  if(e.key!=='j'&&e.key!=='k') return;
+  if(e.ctrlKey||e.metaKey||e.altKey) return;
+  if(typeof _isInteractiveSwipeTarget==='function'&&_isInteractiveSwipeTarget(e.target)) return;
+  e.preventDefault();
+  navigateSession(e.key==='j'?1:-1);
+});

tests/test_3845_keyboard_session_nav.py

@@ -0,0 +1,99 @@
+"""Regression check for #3845 — keyboard session navigation with J/K bindings.
+
+The session list supports keyboard navigation using J (next) and K (previous)
+to move focus through sessions without mouse interaction. Verified at the source
+level so this stays fast.
+"""
+from pathlib import Path
+
+REPO = Path(__file__).parent.parent
+SESSIONS_JS = (REPO / "static" / "sessions.js").read_text(encoding="utf-8")
+
+
+def test_navigateSession_function_exists():
+    """navigateSession function is defined and exported to global scope."""
+    assert "function navigateSession(dir)" in SESSIONS_JS
+
+
+def test_navigateSession_calls_loadSession():
+    """navigateSession calls loadSession(next) when switching sessions."""
+    # Extract the navigateSession function definition
+    start = SESSIONS_JS.index("function navigateSession(dir)")
+    end = SESSIONS_JS.index("}", start) + 1
+    func_body = SESSIONS_JS[start:end]
+    assert "loadSession(next)" in func_body
+
+
+def test_navigateSession_queries_session_items():
+    """navigateSession queries .session-item[data-sid] elements."""
+    start = SESSIONS_JS.index("function navigateSession(dir)")
+    end = SESSIONS_JS.index("}", start) + 1
+    func_body = SESSIONS_JS[start:end]
+    assert ".session-item[data-sid]" in func_body
+
+
+def test_j_k_keydown_listener_exists():
+    """J/K keyboard listener is registered on document."""
+    # Find the keyboard listener that checks for j and k keys
+    assert "if(e.key!=='j'&&e.key!=='k')" in SESSIONS_JS
+
+
+def test_j_k_listener_appears_after_navigateSession():
+    """J/K listener appears after navigateSession function definition."""
+    nav_start = SESSIONS_JS.index("function navigateSession(dir)")
+    jk_start = SESSIONS_JS.index("if(e.key!=='j'&&e.key!=='k')", nav_start)
+    assert jk_start > nav_start
+
+
+def test_j_k_listener_prevents_default():
+    """e.preventDefault() is called before navigateSession in J/K listener."""
+    jk_start = SESSIONS_JS.index("if(e.key!=='j'&&e.key!=='k')")
+    # Extract the J/K listener code block
+    jk_block_end = SESSIONS_JS.index("});", jk_start)
+    jk_block = SESSIONS_JS[jk_start:jk_block_end]
+
+    assert "e.preventDefault()" in jk_block
+    # Verify preventDefault comes before navigateSession call
+    prevent_idx = jk_block.index("e.preventDefault()")
+    nav_idx = jk_block.index("navigateSession")
+    assert prevent_idx < nav_idx
+
+
+def test_j_k_listener_checks_modifiers():
+    """J/K listener ignores when Ctrl, Meta, or Alt modifiers are active."""
+    jk_start = SESSIONS_JS.index("if(e.key!=='j'&&e.key!=='k')")
+    jk_block_end = SESSIONS_JS.index("});", jk_start)
+    jk_block = SESSIONS_JS[jk_start:jk_block_end]
+
+    assert "e.ctrlKey" in jk_block
+    assert "e.metaKey" in jk_block
+    assert "e.altKey" in jk_block
+
+
+def test_j_k_listener_checks_interactive_swipe_target():
+    """J/K listener checks _isInteractiveSwipeTarget to avoid input fields."""
+    jk_start = SESSIONS_JS.index("if(e.key!=='j'&&e.key!=='k')")
+    jk_block_end = SESSIONS_JS.index("});", jk_start)
+    jk_block = SESSIONS_JS[jk_start:jk_block_end]
+
+    assert "_isInteractiveSwipeTarget" in jk_block
+    assert "typeof _isInteractiveSwipeTarget===" in jk_block
+
+
+def test_j_navigates_forward():
+    """Pressing J calls navigateSession with dir=1 (forward)."""
+    jk_start = SESSIONS_JS.index("if(e.key!=='j'&&e.key!=='k')")
+    jk_block_end = SESSIONS_JS.index("});", jk_start)
+    jk_block = SESSIONS_JS[jk_start:jk_block_end]
+
+    assert "navigateSession(e.key==='j'?1:-1)" in jk_block
+
+
+def test_k_navigates_backward():
+    """Pressing K calls navigateSession with dir=-1 (backward)."""
+    jk_start = SESSIONS_JS.index("if(e.key!=='j'&&e.key!=='k')")
+    jk_block_end = SESSIONS_JS.index("});", jk_start)
+    jk_block = SESSIONS_JS[jk_start:jk_block_end]
+
+    # The ternary "e.key==='j'?1:-1" encodes both J and K behavior
+    assert "navigateSession(e.key==='j'?1:-1)" in jk_block