Fix user-context collection, split agent log destinations, widen upload cap

Mapped drives stopped reporting because the user-context path failed silently
in three separate places, and none of them left a trace to read back.

- Probe: launch via -EncodedCommand instead of staging a temp .ps1 and running
  powershell.exe -File. A missing or quarantined script file fails BEFORE any
  statement runs, so the script's own try/catch never sees it and the only
  symptom is exit -196608.
- Spool: pin to the ShopFloor profile. Resolving it through WTSQueryUserToken
  is privileged, endpoint protection blocks it, and on failure the tray
  (writer) and service (reader) silently disagree about the path.
- Spool: consume after a successful parse, so a stopped tray cannot keep
  re-reporting stale mapped drives as current. Unparseable files are left in
  place for the next cycle.
- Logging: user-session components cannot write to Program Files or to the
  SYSTEM-owned ProgramData log directory, and the file sink degrades to a
  silent no-op when it cannot create its directory. Tray and probe now log to
  C:\Users\ShopFloor\ShopDB\Logs, installs transcript to ProgramData, and the
  sink records a SinkProblem instead of swallowing UnauthorizedAccessException.
- Installer: provision the operator spool/log directories with ShopFloor:Modify
  before the tray first runs, and stop the transcript via trap so a throw
  cannot orphan exactly the failed install worth reading.
- Upload cap 64 -> 128 MB: the self-contained tray publishes at ~69 MB and was
  rejected on SIZE, but the size check returns before the PE is parsed, so the
  operator only ever saw a version-detection failure.

AGENT-CONTRACT.md gains a normative section defining the three security
contexts, their log destinations, the fixed spool path and consume-on-read.

Agent 1.8.0 -> 1.8.1, tray 1.1.0 -> 1.1.1 so the deployed build is
identifiable from a log line.

tests/test_plugins/test_endpoints_agentupload.py

@@ -14,6 +14,8 @@ reaches the version gate.
 import io
 
 from plugins.endpoints.api import agentstore
+from plugins.endpoints.api import agentupload
+from shopdb.config import Config
 
 UPLOAD_URL = '/api/endpoints/siteagent/binaries/{}'
 
@@ -63,3 +65,26 @@ def test_upload_rejects_when_neither_typed_nor_pe_is_usable(
     response = _upload(client, auth_headers, monkeypatch, None)
     assert response.status_code == 400
     assert 'dotted-numeric' in response.get_json()['data']['error']['message']
+
+
+def test_upload_cap_admits_a_self_contained_single_file_publish():
+    """The tray publishes ~69 MB; the cap must clear a real binary.
+
+    This is the bug that presented as "upload does not detect version": the
+    size check returns before the PE is parsed, so an oversized file looks
+    like a parser failure to the operator. Pinned at 100 MB rather than the
+    observed 69 MB so runtime growth does not silently re-break it.
+    """
+    assert agentupload._MAX_UPLOAD_BYTES >= 100 * 1024 * 1024
+
+
+def test_request_cap_stays_above_the_agent_upload_cap():
+    """MAX_CONTENT_LENGTH bounds the whole multipart envelope, not the file.
+
+    Setting the two equal rejects a file sitting exactly at the agent cap,
+    because the boundaries and form fields push the request over. They must
+    move together, with real headroom between them.
+    """
+    envelope = Config.MAX_CONTENT_LENGTH
+    assert envelope > agentupload._MAX_UPLOAD_BYTES
+    assert envelope - agentupload._MAX_UPLOAD_BYTES >= 1024 * 1024