refactor: shell integration speaks v2 JSON-RPC on the direct socket path

[arzafran]

What this does

Step 3 of the v1-deletion sequence. The zsh and bash shell-integration scripts (the code injected into every terminal session) talk to the app over a Unix socket to report things like the current directory, git branch, and open PR — until now that direct-socket path sent old-style plain-text lines (report_pwd "/some/path" --tab=X --panel=Y). This switches it to the same JSON-RPC protocol the REMOTE-relay path in the same scripts already speaks, so both transports use one protocol and v1 can eventually be deleted from the app.

Along the way, verifying with bash -n turned up a pre-existing, unrelated bug: _cmux_start_pr_poll_loop in the bash script opened a { ... } block but closed it with ) (a typo from March 2026). That mismatch makes bash fail to parse the entire script, so sourcing programa-bash-integration.bash currently errors out and none of its shell-integration functions get defined at all — confirmed on unmodified origin/main in both bash 3.2 and 5.3. Fixed as its own commit ahead of the JSON-RPC change.

Summary

• Added _cmux_json_rpc_frame() to each script — builds a single-line {"id":1,"method":...,"params":{...}} frame.
• Converted the 8 direct-socket verbs to their v2 equivalents (params per Sources/TerminalController.swift's v2 dispatch):
  • report_tty -> surface.report_tty {workspace_id, tty_name, surface_id?} (surface_id omitted under tmux, matching v1)
  • report_shell_state -> surface.report_shell_state {workspace_id, surface_id, state}
  • report_pwd -> surface.report_pwd {workspace_id, surface_id, path}
  • report_git_branch -> surface.report_git_branch {workspace_id, surface_id, branch, dirty}
  • clear_git_branch -> surface.clear_git_branch {workspace_id, surface_id}
  • report_pr -> surface.report_pr {workspace_id, surface_id, number, url, state, branch}
  • clear_pr -> surface.clear_pr {workspace_id, surface_id}
  • ports_kick -> surface.ports_kick {workspace_id, surface_id?, reason}
• workspace_id/surface_id are sourced from the existing PROGRAMA_WORKSPACE_ID/PROGRAMA_TAB_ID/PROGRAMA_PANEL_ID env vars via the already-present _cmux_relay_workspace_id helper — the same identifiers the v1 fast path and the v2 relay path already use.
• Reused the existing _cmux_json_escape helper (already used by the relay path) rather than adding a new one, so pwd paths / branch names with quotes, backslashes, or unicode are escaped consistently everywhere.
• Fire-and-forget semantics unchanged: _cmux_send/_cmux_send_bg never read a response before this change and still don't; call sites that were synchronous vs. backgrounded stay that way.
• Relay path (_cmux_relay_rpc, _cmux_report_tty_via_relay, etc.) is untouched.
• Both scripts were changed in lockstep to stay behaviorally identical.

Test Plan

• zsh -n Resources/shell-integration/programa-zsh-integration.zsh
• bash -n Resources/shell-integration/programa-bash-integration.bash (on both commits individually, and against unmodified origin/main to confirm the brace bug predates this PR)
• Sourced both scripts in a live shell (bash 3.2 + 5.3, zsh) to confirm they load without error
• Validated generated JSON-RPC frames with python3 -m json.tool, including a nasty path with an apostrophe, embedded quotes, a literal backslash, and unicode (/tmp/it's "here"\there/ünïcödé/日本語) — round-trips correctly for both the zsh and bash escape helpers
• Cannot integration-test against a live app from this environment (repo policy). The real gate is the CI shell-integration Python suite (tests/) and a manual smoke test of shell integration (open a terminal, cd around, check a git branch, open a PR) — recommended before the final v1 removal PR.