fix(plugins): count installs once, and re-resolve the email when the key changes

code.install counted upgrades and repeat sessions. Session start records install
whenever is_first_run() is true, and that only checked whether
telemetry-identity.json exists. Recording install does not create that file —
only the first successful flush does. So install fired for every 0.2.x user on
their first 0.3.x session (0.2.x never wrote the file, and the data directory
survives the upgrade), again for any session starting before that first flush
finished, and — this is the part that makes it unbounded rather than a race —
on every single session, forever, for anyone whose flush never succeeds. An
offline or firewalled user reported a new install every time they opened an
editor, which is exactly the population hardest to see in the data.

A dedicated install-state.json is now claimed with O_CREAT|O_EXCL at the moment
install is recorded, so two sessions starting together cannot both win, and the
marker is not coupled to identity. Deliberately not the identity file: writing
that from a recording process would race the sender, which writes it during
resolve_distinct_id, and overloading it is what caused this.

Upgrade detection keys on the data directory already having content. A fresh
install has an empty one; anything else predates this session. That is a firmer
predicate than looking for 0.2.x's venv/ and requirements.txt, which is a guess
about files another part of the plugin may or may not have written and only ever
works for this one upgrade. The version is stored in the marker so later changes
record code.upgrade with a real from_version.

A cached email outlived an API key change. resolve_distinct_id kept the first
email it resolved and never looked again, so switching to a key from another
account kept attributing events to the previous one. It now stores a fingerprint
of the key the email came from and re-resolves when the current key differs, and
falls back to the anonymous id when no key is configured rather than continuing
to attribute to an account it cannot verify.

The dangerous part is the alias. resolve_distinct_id's second return value
becomes a PostHog $identify with $anon_distinct_id, and aliasing one account
email to another merges two real person profiles irreversibly. The re-resolve
path returns no alias; aliasing runs anonymous to email only, and never
email to email.

One existing test asserted that is_first_run flips when the identity file is
written, which is the defect itself. Rewritten, along with coverage for atomic
claiming, upgrade detection and version changes.

Claude-Session: https://claude.ai/code/session_01C7tEmH86HAr7GoAAKCEHZb

integrations/claude-code-plugin/tests/test_telemetry.py

@@ -265,12 +265,47 @@ def test_an_unresolvable_key_falls_back_to_the_anonymous_id(isolated_env, monkey
     assert telemetry.resolve_distinct_id()[0].startswith("code-anon-")
 
 
-def test_is_first_run_flips_after_the_first_identity_write(isolated_env):
+def test_first_run_is_not_flipped_by_writing_the_identity_file(isolated_env):
+    """The identity file is written by a successful flush, not by recording.
+
+    Keying first-run off it meant an offline user recorded code.install on every
+    session forever, and every 0.2.x user recorded one on their first 0.3.x run.
+    """
     assert telemetry.is_first_run()
     telemetry.anonymous_id()
+    assert telemetry.is_first_run()
+
+
+def test_claiming_install_ends_first_run(isolated_env):
+    assert telemetry.claim_install() == "install"
     assert not telemetry.is_first_run()
 
 
+def test_install_can_only_be_claimed_once(isolated_env):
+    """Two sessions starting together must not both record an install."""
+    assert telemetry.claim_install() == "install"
+    assert telemetry.claim_install() is None
+
+
+def test_a_populated_data_dir_reads_as_an_upgrade(isolated_env):
+    """A fresh install has an empty data directory; anything else predates it."""
+    data_dir = memory_core.data_dir()
+    data_dir.mkdir(parents=True, exist_ok=True)
+    (data_dir / "requirements.txt").write_text("mem0ai\n", encoding="utf-8")
+    assert telemetry.claim_install() == "upgrade"
+
+
+def test_a_version_change_is_claimed_once(isolated_env):
+    telemetry.claim_install()
+    state_path = memory_core.data_dir() / "install-state.json"
+    state = json.loads(state_path.read_text())
+    state["plugin_version"] = "0.0.1-old"
+    state_path.write_text(json.dumps(state), encoding="utf-8")
+
+    assert telemetry.claim_version_change() == "0.0.1-old"
+    assert telemetry.claim_version_change() is None
+
+
 def test_spawn_flush_does_nothing_without_a_spool(isolated_env):
     with patch.object(telemetry.subprocess, "Popen") as popen:
         assert telemetry.spawn_flush() is False