fix(chat): route ALL synthetic backend user rows to system events (#937)

The backend persists a whole class of internal scaffolding as plain
role=user rows with NO display_kind (SessionDB strips underscore metadata):
runtime nudges (max tool-call iterations), context injections ([System:/[CONTEXT/
[PRIOR CONTEXT), background/cron/delegation notices ([IMPORTANT: Background/
Cronjob Response:/[ASYNC DELEGATION), out-of-band markers ([OUT-OF-BAND), and
todo/planning injections ([Your active task list/[Planning state preserved).
These are NOT real human turns, but the mobile rendered them as user bubbles.

Mirror the backend's own synthetic-detection contract
(agent.context_compressor._synthetic_user_row) with a prefix map. Any role=user
row with no display_kind that starts with a known synthetic prefix is routed to
a SystemEvent instead of a user turn. The 90-calls nudge maps to a specific
"Reached tool-call limit" chip; the rest map to a generic "System notice" chip.
Real user messages (no synthetic prefix) are unaffected.

- FullBleedTurns: SYNTHETIC_USER_PREFIX_KINDS map + syntheticSystemKind() that
  tags matched rows so the timeline chip can name them.
- timelineMarkerLabelRes: max_iterations_reached + system_notice labels.
- Strings en/zh/ko for both.
- Tests: assert the new labels map; assert every synthetic prefix routes to a
  SystemEvent (not a user turn); assert a real user message stays a user turn.

The display_kind-tagged events (model/personality switches, auto-continue,
delegation complete, skill invocation, internal notification) are already
handled separately (PR #936, merged).

ktlint + Android Lint + unit tests green locally.

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/test/java/com/m57/hermescontrol/ui/chat/FullBleedTurnsTest.kt

@@ -90,6 +90,25 @@ class FullBleedTurnsTest {
         assertEquals(listOf<ChatTurn>(entries(AgentEntry.SystemEvent(marker))), result)
     }
 
+    @Test
+    fun `max-iterations nudge is a SystemEvent not a user bubble`() {
+        // Backend persists the max-iterations notice as a plain role=user row
+        // with NO display_kind (it's stripped on SessionDB persistence); the
+        // mobile must still treat it as a system event so it renders with the
+        // distinct system design instead of a fake user bubble.
+        val content =
+            "You've reached the maximum number of tool-calling iterations allowed. " +
+                "Please provide a final response."
+        val nudge = msg("n1", MessageRole.USER, content = content)
+        val result = groupIntoTurns(listOf(nudge))
+        assertEquals(
+            listOf<ChatTurn>(
+                entries(AgentEntry.SystemEvent(nudge.copy(displayKind = "max_iterations_reached"))),
+            ),
+            result,
+        )
+    }
+
     @Test
     fun `marker between assistant and user does not close the agent turn`() {
         val a = msg("a1", MessageRole.ASSISTANT)

app/src/test/java/com/m57/hermescontrol/ui/chat/fullbleed/TimelineMarkerTest.kt

@@ -26,6 +26,10 @@ class TimelineMarkerTest {
             R.string.timeline_marker_internal_notification,
             timelineMarkerLabelRes("internal_notification"),
         )
+        assertEquals(
+            R.string.timeline_marker_max_iterations,
+            timelineMarkerLabelRes("max_iterations_reached"),
+        )
     }
 
     @Test