fix(plugins): stamp surface identity at record time, not send time

Six defects in 0.3.x plugin telemetry. Defects 1, 2 and 6 were not three bugs:
they were one spool protocol getting three properties wrong.

Identity was decided by the wrong process. `harness` was stamped in record(),
correctly, but `source` was read from a module global in flush() — so whichever
process drained the spool named every event in it. Two processes never call
init(): mcp_server.py, and the detached `python3 telemetry.py` sender that
spawn_flush() starts. record() now stamps source beside harness, and the build
generates core/_harness_id.py per host so identity resolves with no init() call
at all. That also unifies two defaults that disagreed (`<host>_plugin` vs
`MEM0_<HOST>_PLUGIN`), which could yield three source values for one plugin.

Ownership was inferred, not held. Path.replace is os.rename, which preserves
mtime, so a claim made after a quiet minute inherited the spool's age and was
stealable the instant it existed. Claims are touched on creation and the
per-batch rewrite doubles as a lease heartbeat.

Progress was not durable. flush() returned on the first failed batch without
truncating, so the retry re-posted from index 0 — 150 events delivered 250
times. It now rewrites the claim with the unsent remainder after every batch,
bounding a crash to one repeated batch, and each event carries a uuid.

Parked batches starved. They were only reachable when no spool existed, and
because sessions keep recording there usually was one, so a batch parked by a
failed send waited until the 7-day expiry deleted it unsent — despite its own
presence being what starts the sender. flush() drains them in the same run, and
expiry now applies only after a genuine retry has failed.

code.install counted upgrades and repeat sessions. is_first_run() read the
identity file, which only a successful flush writes, so an offline user recorded
an install every session forever. A dedicated install-state.json is claimed
atomically at record time; a non-empty data directory reads as an upgrade.

The docs called this anonymous. Every event carries the account email, and the
hashes were unsalted SHA-256 over a git remote URL or an absolute path
containing the username. READMEs, the module docstring and a new docs section
now say what the code does, and repo/session digests are salted per install.

A cached email outlived an API key change. It is now re-resolved when the key's
fingerprint differs, and $identify aliases anonymous->email only — aliasing one
account to another merges person profiles irreversibly.

All six shipped green because the shared core's only tests lived under one host,
behind a conftest that calls init() at import. Core behaviour was never
exercised uninitialised. Adds agent-plugin-core/tests with no init, including
subprocess tests and coverage for the portable plugin, which has no flush worker
and would pass a native-only test vacuously.

Also puts the three surface headers on the SDKs, CLIs and integrations, and
corrects a README claiming ZAPIER/STRANDS were already in the platform allowlist.

Verified: 59 core tests, 203 claude-code, 11 cursor, 5 codex, 2 kimi, 6
antigravity. ruff and compileall clean. --check clean for all six hosts.
TypeScript changes are not typechecked locally (deps not installed).

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

integrations/agent-plugin-core/build/build.py

@@ -81,6 +81,28 @@ def replace_output(staged: Path, output: Path) -> Path:
     return output
 
 
+def _render_harness_id(host: str) -> str:
+    """Emit core/_harness_id.py for one host.
+
+    Carries both vocabularies from a single definition: the PostHog `source` tag
+    and the platform's X-Mem0-Source / X-Application pair. Keeping them together
+    is what stops the two from drifting into separate vocabularies for the same
+    thing.
+    """
+    tag = host.upper().replace("-", "_") + "_PLUGIN"
+    return (
+        '"""Generated by integrations/agent-plugin-core/build/build.py. Do not edit."""\n'
+        "\n"
+        f'HARNESS_ID = "{host}"\n'
+        f'SOURCE_TAG = "{tag}"\n'
+        "\n"
+        "# Platform-side vocabulary (mem0_event.source + X-Application). The whole\n"
+        "# plugin family is one source; which editor it runs in is the application.\n"
+        'PLATFORM_SOURCE = "MEM0_PLUGIN"\n'
+        f'PLATFORM_APPLICATION = "{host}"\n'
+    )
+
+
 def _bundle_python(
     staged: Path,
     host: str,
@@ -96,6 +118,12 @@ def _bundle_python(
             continue
         shutil.copy2(source, core / source.name)
 
+    # Generated per host so identity does not depend on an entrypoint remembering
+    # to call telemetry.init(). mcp_server.py and the detached telemetry.py sender
+    # never did, which is how MCP searches reported harness=generic and every
+    # batch they drained was labelled MEM0_PLUGIN regardless of the real host.
+    (core / "_harness_id.py").write_text(_render_harness_id(host), encoding="utf-8")
+
     values = {
         "PLUGIN_ROOT": plugin_root,
         "PLUGIN_DATA": "${PLUGIN_DATA}",