feat!: remove the v1 line-based socket protocol

[arzafran]

What this does

Programa's terminal socket has spoken two protocols side by side: an old space-delimited
line protocol ("v1") and a newer JSON-RPC protocol ("v2"). Every consumer — the CLI, the
shell integration, the automated tests, and the remote daemon — now speaks v2 exclusively,
so this PR deletes the old protocol and everything that only existed to serve it.

Breaking change for anyone with custom scripts: if you (or a script, alias, or tool)
talk to Programa's socket directly with the old space-delimited commands (list_windows,
focus_window "id", report_pwd ..., etc.) instead of through the programa CLI, those
commands will now get a JSON error (v1_removed) instead of a response. Everyone using the
programa CLI is already unaffected — it moved to v2 in #74.

Summary

• TerminalController.processCommand now dispatches JSON unconditionally. A non-JSON line
  gets a terse v1_removed JSON error pointing at the v2 protocol instead of being routed
  into the old ~90-case command switch.
• Deleted the v1 switch and every handler function that became unreferenced once it was
  gone, along with their v1-only argument-parsing helpers (parseOptions/
  parseOptionsNoStop, resolveTabForReport, withReportTargetSurface,
  upsertSidebarMetadata/clearSidebarMetadata/listSidebarMetadata,
  schedulePanelMetadataMutation, parseReadScreenArgs, plus two small structs used only
  by read_screen argument parsing).
• Kept as shared helpers — verified each still has a live v2 caller before touching it:
  • setShortcut, simulateShortcut, activateApp, isTerminalFocused, readTerminalText,
    renderStats, layoutDebug, bonsplitUnderflowCount/resetBonsplitUnderflowCount,
    emptyPanelCount/resetEmptyPanelCount, focusFromNotification, flashCount/
    resetFlashCounts, panelSnapshot/panelSnapshotReset, captureScreenshot — each of
    v2's debug.* methods calls straight into these as its implementation core, so the old
    v1-named function stayed even though its switch case line is gone.
  • Self.socketFastPathState (the shell-activity dedup state) and
    tailTerminalLines/readTerminalTextBase64(terminalPanel:...) — used directly by
    v2SurfaceReportShellState and v2SurfaceReadText/screen-snapshot code respectively.
• Auth resolution: auth was never actually a v1 switch command in the way the rest of
  the protocol was — authResponseIfNeeded intercepts auth <password> (v1-style line) and
  auth.login (v2 JSON-RPC) as a connection-level preamble before any protocol dispatch,
  and both paths already did real password verification. The only wrinkle: the v1 switch had
  a fallback case "auth" that answered "OK: Authentication not required" for the (fairly
  common) case where the CLI has a locally-resolvable password but the server's access mode
  doesn't actually require one — deleting the switch would have made the CLI's raw auth <password> line hit the new v1_removed error and fail auth in that case. Fixed by
  migrating the CLI's auth call (CLI/programa.swift) from the raw auth <password> line to
  auth.login — the v2 protocol already has a symmetric fallback case for the "not required"
  scenario (v2's auth.login case returns authenticated: true, required: false), so no new
  server-side method was needed, only the client-side call.
• Removed the now-dead isV2: false branch's backing data (focusIntentV1Commands) from the
  socket focus-mutation policy, since no code path can produce isV2: false for a real
  command anymore. Updated the one unit test that exercised that branch by v1 command name to
  cover the v2 equivalent instead (window.focus, debug.shortcut.simulate).
• Docs: docs/v2-api-migration.md collapses from a migration-tracking doc into a short
  "v1 was removed" note that keeps the v1->v2 method-name mapping table for anyone reading old
  scripts or commits. docs/socket-focus-steal-audit.todo.md and
  docs/agent-browser-port-spec.md (both are audit/planning docs from the earlier migration)
  get a short annotation marking their v1-specific sections historical, without rewriting
  their audit trail. CLAUDE.md's socket-threading-policy examples are reworded from v1
  command names (report_*) to their v2 equivalents (surface.report_*) — the policy itself
  is unchanged, it always governed v2 telemetry too.

Line delta: Sources/TerminalController.swift goes from 12834 to 9615 lines (-3219).
Net repo diff: +156 / -3410 across 7 files.

Test Plan

• xcodebuild ... -scheme programa -- BUILD SUCCEEDED
• xcodebuild ... -scheme programa-cli -- BUILD SUCCEEDED
• xcodebuild ... -scheme programa-unit build-for-testing -- TEST BUILD SUCCEEDED
• Grepped programaTests/ for every deleted function name -- the handful of matches are
  all unrelated identically-named methods on other types (TabManager.closeWorkspace,
  KeyboardShortcutSettings.setShortcut, AppDelegate.moveWorkspaceToWindow, etc.), not
  calls into the deleted TerminalController wrappers (which were private to that
  file, so cross-file access was never possible) -- confirmed by the test target
  compiling cleanly.
  • programaTests/TerminalControllerSocketSecurityTests.swift: updated
    testSocketCommandPolicyDistinguishesFocusIntent (see above); left
    testPasswordModeRejectsUnauthenticatedCommands untouched since it only exercises the
    pre-protocol auth gate, which is unaffected by this change.
• tests_v2/ is the CI gate for full runtime verification (never run locally per repo
  policy). Traced through the relevant tests by hand: test_cli_global_flags_and_v1_error_contract.py's
  ping calls already go through the CLI's v2 system.ping, and its implicit auth call
  (via SocketPasswordResolver) now goes through the migrated auth.login path -- both
  unaffected by the v1 deletion.

Not merging -- please review.