test(system): compare Diagnostics & logs with the concept

System › Diagnostics & logs and its log cleanup review are compared with the
concept (app.js 694–695 and maintenancePlan("rotated logs")) in both themes at
1600x1100 and 390x844, with D109 and D110 (and D100 for the review) as the only
mapped differences, a 320-wide select check and a mutation check.

The fixture gains a concept seed mode (the concept's four log lines, a 1.4 MB
active log with three rotated copies, console logging off), and the plan
dialog's measureReview and mapPlanConcept move unchanged into
concept-inventory.mjs for Maintenance and this review.

The comparison found that the Database line read a report key that does not
exist (database_info.size_bytes) and so always showed "0 bytes"; it now reads
database_size_bytes, the key get_database_info() returns.

Part of #329

tests/browser/workspace_diagnostics_fixture.py

@@ -14,7 +14,11 @@ real log folder. Every route refuses a log folder outside the server root.
   more INFO records older still), ``active`` bytes into the active log,
   rotated copies ``prompt_manager.log.<n>`` of the listed sizes (fixed
   times), on POSIX a symlink ``prompt_manager.log.<n+1>`` to a file outside
-  the folder (``link``) and a user's ``prompt_manager.log.bak`` (``other``);
+  the folder (``link``) and a user's ``prompt_manager.log.bak`` (``other``).
+  ``{mode: "concept"}`` reproduces the concept's Logs sample (app.js 695)
+  for the comparison: the buffer holds only its four lines, the active log
+  is 1.4 MB with three rotated copies ("prompt_manager.log · 1.4 MB · rotated
+  copies: 3") and console logging is off, as the concept's toggle;
 - ``POST /__test__/logs/rotate`` rolls the copies over as the handler does
   (``.2`` → ``.3``, ``.1`` → ``.2``, a new ``.1``), so a reviewed plan no
   longer matches;
@@ -48,6 +52,10 @@ LEVEL_RECORDS = (
     ("09:30:03", logging.CRITICAL, "The database could not be opened"),
 )
 ROTATED_TIME = datetime.datetime(2026, 10, 25, 14, 2)
+# The concept's "prompt_manager.log · 1.4 MB · rotated copies: 3": the active
+# log stays under 1.45 MB while the server writes its own lines.
+CONCEPT_ACTIVE = int(1.4 * 1024 * 1024)
+CONCEPT_ROTATED = (3072, 2048, 1024)
 MAX_SEED_BYTES = 64 * 1024 * 1024
 DEFAULT_CONFIG = {
     "level": "INFO",
@@ -135,7 +143,25 @@ def register_diagnostics_commands(app, routes, api, root: Path):
         with manager._buffer_lock:
             manager._log_buffer.clear()
 
+    def seed_concept() -> None:
+        manager = _manager()
+        log_dir = folder()
+        manager.update_config({"console_logging": False})
+        with manager._buffer_lock:
+            manager._log_buffer.clear()
+        for index, (time_text, level, message) in enumerate(CONCEPT_RECORDS):
+            record = _record(time_text, level, message, index)
+            manager.add_to_buffer(record, record.getMessage())
+        with open(log_dir / ACTIVE, "ab") as handle:
+            handle.write(b"x" * CONCEPT_ACTIVE)
+        for number, size in enumerate(CONCEPT_ROTATED, start=1):
+            moment = ROTATED_TIME - datetime.timedelta(hours=number)
+            _touch(log_dir / f"{ACTIVE}.{number}", size, moment)
+
     def seed(data) -> None:
+        if data.get("mode") == "concept":
+            seed_concept()
+            return
         manager = _manager()
         log_dir = folder()
         with_records = data.get("records", True) is not False