Land staged session/MCP/chrome work + sidebar clear-J fix

This batches the in-flight [Unreleased] block from CHANGELOG.md into a
single commit. Highlights:

- Real MCP protocol layer (initialize / tools/list / tools/call) so
  vendor MCP clients can complete the handshake against the per-PID
  socket. Legacy direct-dispatch preserved for the harness.
- New mcp_injection kinds — cli_override for codex, config_env for
  opencode — joining the existing env-var and config_file paths so
  patterm can slot into more agents without touching their real
  config or auth.
- Ctrl+A/D and Ctrl+W/S focus navigation across tabs and intra-tab
  process lists, recognised in legacy / kitty CSI u / xterm
  modifyOtherKeys encodings.
- Palette macros (sw / k / sp ) and reordering so open sessions
  surface above spawn-new entries.
- Two-row tab bar, sidebar/tabbar/status chrome cache, viewport-wipe
  on agent spawn, CR-terminated orchestrator injections, and split-
  Enter PTY writes so paste-detecting TUIs see Enter as a key event.

Also fixes the bug logged in TODO: claude's Ctrl+O tool-call expansion
emits CSI 0 J, which the viewport renderer was forwarding verbatim —
wiping the sidebar to the right of the cursor and leaving the chrome
cache convinced nothing had changed. CSI 0 J and CSI 1 J are now
translated into per-row ECH sequences clamped to the viewport, same
as CSI 2 J and CSI K already were.

Agent guides (CLAUDE.md / AGENTS.md) now spell out the
TODO->CHANGELOG workflow so completed items land in the changelog
rather than as ticked entries left behind in TODO.

internal/app/palette.go

@@ -38,6 +38,29 @@ type paletteState struct {
 	items []paletteItem
 }
 
+// macroPrefixes maps the palette macro prefix (without trailing space)
+// to the paletteAction.kind values that should be retained when that
+// macro is active. Typing `sw <query>` filters to switch entries only,
+// `k <query>` to kills, `sp <query>` to spawn entries (agents +
+// processes).
+var macroPrefixes = map[string][]string{
+	"sw": {"switch"},
+	"k":  {"kill"},
+	"sp": {"spawn-agent", "spawn-process"},
+}
+
+// detectMacro returns the macro keyword and the remaining query, or
+// ("", original) if no macro is active. A macro is active when the
+// query starts with one of the known prefixes followed by a space.
+func detectMacro(q string) (macro, rest string) {
+	for k := range macroPrefixes {
+		if len(q) > len(k) && q[:len(k)] == k && q[len(k)] == ' ' {
+			return k, q[len(k)+1:]
+		}
+	}
+	return "", q
+}
+
 func newPalette(children []*Child, focused string, presets preset.Set) *paletteState {
 	p := &paletteState{children: children, focused: focused, presets: presets}
 	p.rebuild()
@@ -47,6 +70,21 @@ func newPalette(children []*Child, focused string, presets preset.Set) *paletteS
 func (p *paletteState) rebuild() {
 	all := p.allItems()
 	q := strings.ToLower(string(p.query))
+	macro, rest := detectMacro(q)
+	if macro != "" {
+		kinds := macroPrefixes[macro]
+		filtered := all[:0:0]
+		for _, it := range all {
+			for _, k := range kinds {
+				if it.action.kind == k {
+					filtered = append(filtered, it)
+					break
+				}
+			}
+		}
+		all = filtered
+		q = rest
+	}
 	if q == "" {
 		p.items = all
 	} else {
@@ -68,8 +106,32 @@ func (p *paletteState) rebuild() {
 func (p *paletteState) allItems() []paletteItem {
 	var out []paletteItem
 
-	// Preset commands first — SPEC §4 calls these out as the primary
-	// way to spawn anything. One entry per file under presets/.
+	// Switch entries first — existing open agents/processes should
+	// surface above options to spawn new ones. Hide non-running agents
+	// (e.g. killed ones) so the list doesn't accumulate corpses. Command
+	// processes are session-persistent, so they remain visible after
+	// exit to keep restart_process in reach.
+	for _, c := range p.children {
+		if c.Kind == KindAgent && c.Status() != StatusRunning {
+			continue
+		}
+		label := "Switch to " + c.Name
+		hint := strings.Join(c.Argv, " ")
+		if c.ID == p.focused {
+			label = "• " + label + " (current)"
+		}
+		if c.Status() != StatusRunning {
+			label = label + "  [" + string(c.Status()) + "]"
+		}
+		out = append(out, paletteItem{
+			label:  label,
+			hint:   hint,
+			action: paletteAction{kind: "switch", childID: c.ID},
+		})
+	}
+
+	// Preset commands — SPEC §4 calls these out as the primary way to
+	// spawn anything. One entry per file under presets/.
 	for _, pr := range p.presets.Agents {
 		out = append(out, paletteItem{
 			label:  "Spawn agent: " + pr.Name,
@@ -85,22 +147,7 @@ func (p *paletteState) allItems() []paletteItem {
 		})
 	}
 
-	// Switch / Kill entries — one per existing child.
-	for _, c := range p.children {
-		label := "Switch to " + c.Name
-		hint := strings.Join(c.Argv, " ")
-		if c.ID == p.focused {
-			label = "• " + label + " (current)"
-		}
-		if c.Status() != StatusRunning {
-			label = label + "  [" + string(c.Status()) + "]"
-		}
-		out = append(out, paletteItem{
-			label:  label,
-			hint:   hint,
-			action: paletteAction{kind: "switch", childID: c.ID},
-		})
-	}
+	// Kill entries last among the action rows, before Quit.
 	for _, c := range p.children {
 		if c.Status() != StatusRunning {
 			continue
@@ -447,7 +494,7 @@ func (p *paletteState) render(out writeFlusher, cols, rows int) {
 	b.WriteString(styleBorder + "├" + strings.Repeat("─", width-2) + "┤" + styleReset)
 	row++
 
-	footer := "↵ run  ·  esc close  ·  ↑↓ navigate"
+	footer := "↵ run  ·  esc close  ·  ↑↓ navigate  ·  sw/k/sp <q> filter"
 	fLen := utf8.RuneCountInString(footer)
 	fPad := content - fLen
 	if fPad < 0 {