feat(writes): enable write actions by default (opt-out)

Invert the global write toggle so writes are ENABLED by default and the
user opts OUT, while keeping all other safety intact (per-call confirm=true
dry-run preview and the on-disk audit log are unchanged).

- writes.py: use a `writes_disabled` flag file instead of `writes_enabled`;
  `writes_enabled()` returns True unless the flag exists (env var still
  honored either way); `set_writes(False)` creates the flag, `set_writes(True)`
  removes it. Update user-facing notes.
- tests: default is now ENABLED; adjust toggle/disabled tests (set disabled
  explicitly via set_writes(False) or FAMILIAR_ENABLE_WRITES=0).
- README.md / CLAUDE.md: document writes are on by default, opt out via
  `familiar writes disable`.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_comms.py

@@ -46,7 +46,7 @@ def test_send_mail_dry_run_does_not_post(mock_esi, fake_auth):
 
 def test_send_mail_disabled_raises(mock_esi, fake_auth, tmp_path, monkeypatch):
     monkeypatch.setenv("FAMILIAR_DATA_DIR", str(tmp_path))
-    monkeypatch.delenv("FAMILIAR_ENABLE_WRITES", raising=False)
+    monkeypatch.setenv("FAMILIAR_ENABLE_WRITES", "0")
     mock_esi(lambda r: httpx.Response(201, json=1))
     with pytest.raises(writes.WriteDisabled):
         asyncio.run(comms.send_mail(99, [{"recipient_id": 1}], "s", "b", confirm=True))

tests/test_contacts_fittings.py

@@ -70,7 +70,7 @@ def test_get_fittings(mock_esi, fake_auth):
 
 def test_create_fitting_disabled_raises(mock_esi, fake_auth, tmp_path, monkeypatch):
     monkeypatch.setenv("FAMILIAR_DATA_DIR", str(tmp_path))
-    monkeypatch.delenv("FAMILIAR_ENABLE_WRITES", raising=False)
+    monkeypatch.setenv("FAMILIAR_ENABLE_WRITES", "0")
     mock_esi(lambda r: httpx.Response(201, json={"fitting_id": 5}))
     with pytest.raises(writes.WriteDisabled):
         asyncio.run(fittings.create_fitting(99, {"name": "x"}, confirm=True))

tests/test_writes.py

@@ -19,15 +19,15 @@ async def _exec():
     return {"ok": True}
 
 
-def test_disabled_by_default(tmp_data):
-    assert writes.writes_enabled() is False
+def test_enabled_by_default(tmp_data):
+    assert writes.writes_enabled() is True
 
 
 def test_toggle_on_disk(tmp_data):
-    writes.set_writes(True)
-    assert writes.writes_enabled() is True
     writes.set_writes(False)
     assert writes.writes_enabled() is False
+    writes.set_writes(True)
+    assert writes.writes_enabled() is True
 
 
 def test_env_override(tmp_data, monkeypatch):
@@ -50,12 +50,18 @@ def test_dry_run_does_not_execute(tmp_data):
 
 
 def test_confirm_but_disabled_raises(tmp_data):
+    writes.set_writes(False)
+    with pytest.raises(writes.WriteDisabled):
+        asyncio.run(writes.guard("send_mail", {}, confirm=True, execute=_exec))
+
+
+def test_confirm_but_disabled_via_env_raises(tmp_data, monkeypatch):
+    monkeypatch.setenv("FAMILIAR_ENABLE_WRITES", "0")
     with pytest.raises(writes.WriteDisabled):
         asyncio.run(writes.guard("send_mail", {}, confirm=True, execute=_exec))
 
 
 def test_confirm_enabled_executes_and_audits(tmp_data):
-    writes.set_writes(True)
     result = asyncio.run(writes.guard("send_mail", {"subject": "hi"}, confirm=True, execute=_exec))
     assert result["executed"] is True
     assert result["result"] == {"ok": True}