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/preset/preset.go

@@ -45,16 +45,33 @@ type Preset struct {
 	ChromeTrimHints  []string      `json:"chrome_trim_hints,omitempty"`
 }
 
-// MCPInjection covers the three strategies SPEC §10 enumerates: a CLI
-// flag (claude --mcp-config ...), an external config file we merge into
-// (codex ~/.codex/config.toml), or an env var.
+// MCPInjection covers the strategies SPEC §10 enumerates plus
+// `cli_override` for agents (like codex) that accept inline config
+// overrides via repeated CLI flags, and `config_env` for agents (like
+// opencode) that read their config from an env var. The fields used
+// depend on Kind.
 type MCPInjection struct {
-	Kind       string `json:"kind"` // "flag" | "config_file" | "env_var"
+	Kind       string `json:"kind"` // "flag" | "config_file" | "env_var" | "cli_override" | "config_env"
 	Flag       string `json:"flag,omitempty"`
 	ConfigPath string `json:"config_path,omitempty"`
-	Path       string `json:"path,omitempty"`
-	MergeKey   string `json:"merge_key,omitempty"`
 	Var        string `json:"var,omitempty"`
+
+	// config_file fields. patterm reads the file at Path, merges in a
+	// `patterm` entry under MergeKey, writes the result inside a temp
+	// directory laid out so HomeVar + HomePath points at the merged
+	// file, and exports HomeVar to the child. Format is inferred from
+	// Path's extension (toml or json) when blank.
+	Path     string `json:"path,omitempty"`
+	MergeKey string `json:"merge_key,omitempty"`
+	Format   string `json:"format,omitempty"`
+	HomeVar  string `json:"home_var,omitempty"`
+	HomePath string `json:"home_path,omitempty"`
+
+	// cli_override fields. patterm emits one `<Flag> <KeyPrefix>.<k>=<v>`
+	// pair per MCP setting (command, args) so the agent merges them
+	// into its in-memory config without touching any file on disk. Used
+	// for codex's `-c key=value`.
+	KeyPrefix string `json:"key_prefix,omitempty"`
 }
 
 // ReadySignal lets a preset override the default 1s-idle heuristic.
@@ -196,7 +213,12 @@ func ensureDefaults(base string) error {
 			`{
   "name": "codex",
   "argv": ["codex"],
-  "mcp_injection": { "kind": "config_file", "path": "~/.codex/config.toml", "merge_key": "mcp_servers" },
+  "mcp_injection": {
+    "kind": "cli_override",
+    "flag": "-c",
+    "key_prefix": "mcp_servers.patterm",
+    "format": "toml"
+  },
   "ready_signal": { "idle_ms": 1000 },
   "chrome_trim_hints": [
     "^OpenAI Codex",
@@ -213,7 +235,13 @@ func ensureDefaults(base string) error {
 			`{
   "name": "opencode",
   "argv": ["opencode"],
-  "mcp_injection": { "kind": "config_file", "path": "~/.config/opencode/opencode.json", "merge_key": "mcp" },
+  "mcp_injection": {
+    "kind": "config_env",
+    "path": "~/.config/opencode/opencode.json",
+    "merge_key": "mcp",
+    "format": "json",
+    "var": "OPENCODE_CONFIG_CONTENT"
+  },
   "ready_signal": { "idle_ms": 1000 },
   "chrome_trim_hints": [
     "^\\s*█",