neo(feat[fields]): Re-expose 8 version-gated tokens added after tmux 3.2a

why: with the scope+version gating in place, the format string sent to
older tmux versions automatically excludes tokens that those versions
don't recognize. The 8 tokens below first registered in tmux 3.4-3.6 —
tagging them with FIELD_VERSION makes them appear on supported tmux
releases that include them, and absent on older tmux without sending
unknown tokens that bloat the format string or trigger crashes.

what:
- src/libtmux/neo.py:
  - Re-add 8 fields to Obj alphabetically: pane_key_mode,
    pane_unseen_changes, session_active, session_activity_flag,
    session_alert, session_bell_flag, session_silence_flag, client_theme.
  - Populate FIELD_VERSION with each token's minimum tmux release
    (3.4 for pane_unseen_changes, 3.5 for pane_key_mode, 3.6 for the
    five session_* tokens and client_theme).
- tests/test_pane.py: restore pane_key_mode and pane_unseen_changes in
  PANE_FORMAT_FIELDS (the parametrized declaration+hydration test).
- tests/test_session.py: restore the 5 new session_* entries in
  SESSION_FORMAT_FIELDS.

Verification:
- On tmux 3.6a (local), all 8 tokens hydrate via refresh(); 1182 tests
  pass.
- On tmux 3.2a, FIELD_VERSION skips all 8 — the -F template stays at
  its pre-PR-#672-rollback shape for that version.

Version anchors verified via:
  rg '"<token>"' ~/study/c/tmux-3.<N>a/format.c
across 3.2a, 3.3a, 3.4, 3.5, 3.5a, 3.6, 3.6a.

Author: tony

src/libtmux/neo.py

@@ -42,7 +42,17 @@
 """
 
 
-FIELD_VERSION: dict[str, str] = {}
+FIELD_VERSION: dict[str, str] = {
+    # Post-3.2a additions (verified via ~/study/c/tmux-3.<N>a/format.c).
+    "pane_unseen_changes": "3.4",
+    "pane_key_mode": "3.5",
+    "session_active": "3.6",
+    "session_activity_flag": "3.6",
+    "session_alert": "3.6",
+    "session_bell_flag": "3.6",
+    "session_silence_flag": "3.6",
+    "client_theme": "3.6",
+}
 """Minimum tmux version that registers each format token.
 
 Field names absent from this dict default to ``"3.2a"`` (always-safe within
@@ -186,6 +196,7 @@ class Obj:
     client_termfeatures: str | None = None
     client_termname: str | None = None
     client_termtype: str | None = None
+    client_theme: str | None = None
     client_tty: str | None = None
     client_uid: str | None = None
     client_user: str | None = None
@@ -240,6 +251,7 @@ class Obj:
     pane_in_mode: str | None = None
     pane_index: str | None = None
     pane_input_off: str | None = None
+    pane_key_mode: str | None = None
     pane_last: str | None = None
     pane_left: str | None = None
     pane_marked: str | None = None
@@ -257,6 +269,7 @@ class Obj:
     pane_title: str | None = None
     pane_top: str | None = None
     pane_tty: str | None = None
+    pane_unseen_changes: str | None = None
     pane_width: str | None = None
     pid: str | None = None
     scroll_position: str | None = None
@@ -267,10 +280,14 @@ class Obj:
     selection_end_y: str | None = None
     selection_start_x: str | None = None
     selection_start_y: str | None = None
+    session_active: str | None = None
     session_activity: str | None = None
+    session_activity_flag: str | None = None
+    session_alert: str | None = None
     session_alerts: str | None = None
     session_attached: str | None = None
     session_attached_list: str | None = None
+    session_bell_flag: str | None = None
     session_created: str | None = None
     session_format: str | None = None
     session_group: str | None = None
@@ -286,6 +303,7 @@ class Obj:
     session_marked: str | None = None
     session_name: str | None = None
     session_path: str | None = None
+    session_silence_flag: str | None = None
     session_stack: str | None = None
     session_windows: str | None = None
     socket_path: str | None = None

tests/test_pane.py

@@ -612,13 +612,15 @@ def test_send_keys_flag_only_requires_a_flag(session: Session) -> None:
     "pane_format",
     "pane_in_mode",
     "pane_input_off",
+    "pane_key_mode",
     "pane_last",
     "pane_marked",
     "pane_marked_set",
     "pane_mode",
     "pane_path",
     "pane_pipe",
     "pane_synchronized",
+    "pane_unseen_changes",
 )
 
 

tests/test_session.py

@@ -709,12 +709,17 @@ def test_session_search_panes_filter_by_id(session: Session) -> None:
 
 
 SESSION_FORMAT_FIELDS = (
+    "session_active",
+    "session_activity_flag",
+    "session_alert",
+    "session_bell_flag",
     "session_format",
     "session_group_attached_list",
     "session_group_many_attached",
     "session_grouped",
     "session_many_attached",
     "session_marked",
+    "session_silence_flag",
 )