feat(#530): server-backed session search (FTS5) (#555)

* feat(#530): add SessionSearch models + searchSessions endpoint + contract tests

* feat(#530): wire server-backed search into Sessions screen (debounce + render)

* style(#530): ktlint import ordering on HermesApiService

* fix(#530): ktlint-clean overlap wrap + map search snippet to title

* fix(#530): map search snippet to title so results show + highlight

* fix(#530): render search hits as honest result cards instead of faking title

Backend SessionSearchResult carries no session name (only snippet + metadata),
so mapping snippet->title made the card show raw excerpt as the title. Instead,
render a dedicated SearchResultCard: 'Match' label + session id, highlighted
snippet as body, and source/model/played-at chips. Added SessionInfo.model and
a friendly relative-time formatter. ktlint clean, compileDebugKotlin + unit
tests pass.

* fix(#530): strip JSON from search snippet + tighten result card padding

* fix(#530): strip FTS highlight markers from search snippet on client

agy's backend change re-wraps matched terms in >>>term<<< markers inside the
clean snippet, but the mobile highlights by raw query term and never consumed
those markers — so literal '>>>'/'<<<' would render in result text. Strip the
markers before passing the snippet to highlightText so the query highlight
still works on clean text.

* fix(#530): integrate tree-flattening hierarchy with search modes in SessionsScreen

* fix(#530): fix test assertion and mock ApiClient in SessionsViewModelTest

* fix(#530): resolve compose PaddingValues compile error and fix slash-preservation test path

* fix(#530): clean search snippet from JSON payload and add unit test

---------

Co-authored-by: M57 <m57@hermes-control.app>

app/src/test/java/com/m57/hermescontrol/ui/sessions/SessionsViewModelTest.kt

@@ -0,0 +1,93 @@
+package com.m57.hermescontrol.ui.sessions
+
+import com.m57.hermescontrol.data.remote.ApiClient
+import com.m57.hermescontrol.data.remote.HermesApiService
+import io.mockk.every
+import io.mockk.mockk
+import io.mockk.mockkObject
+import io.mockk.unmockkAll
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.StandardTestDispatcher
+import kotlinx.coroutines.test.advanceTimeBy
+import kotlinx.coroutines.test.advanceUntilIdle
+import kotlinx.coroutines.test.resetMain
+import kotlinx.coroutines.test.setMain
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Test
+
+@OptIn(ExperimentalCoroutinesApi::class)
+class SessionsViewModelTest {
+    private val testDispatcher = StandardTestDispatcher()
+    private val mockApi = mockk<HermesApiService>(relaxed = true)
+
+    private fun createViewModel(): SessionsViewModel {
+        val vm = SessionsViewModel()
+        testDispatcher.scheduler.advanceUntilIdle()
+        return vm
+    }
+
+    @Before
+    fun setUp() {
+        Dispatchers.setMain(testDispatcher)
+        mockkObject(ApiClient)
+        every { ApiClient.hermesApi } returns mockApi
+    }
+
+    @After
+    fun tearDown() {
+        Dispatchers.resetMain()
+        unmockkAll()
+    }
+
+    @Test
+    fun `blank query resets search mode`() {
+        val vm = createViewModel()
+        vm.setSearchQuery("something")
+        vm.setSearchQuery("")
+        testDispatcher.scheduler.advanceUntilIdle()
+        assertEquals("", vm.uiState.value.searchQuery)
+        assertFalse(vm.uiState.value.isSearchMode)
+        assertEquals(0, vm.uiState.value.searchResults.size)
+        assertFalse(vm.uiState.value.isSearching)
+    }
+
+    @Test
+    fun `non-blank query enters search mode and resolves`() {
+        val vm = createViewModel()
+        vm.setSearchQuery("hello")
+        // state is set synchronously
+        assertEquals("hello", vm.uiState.value.searchQuery)
+        assertTrue(vm.uiState.value.isSearchMode)
+        // advance past debounce + (failing, offline) network call
+        testDispatcher.scheduler.advanceTimeBy(500)
+        testDispatcher.scheduler.advanceUntilIdle()
+        // Either way the spinner must stop and the query persists.
+        assertFalse(vm.uiState.value.isSearching)
+        assertEquals("hello", vm.uiState.value.searchQuery)
+    }
+
+    @Test
+    fun `select all uses the IDs shown in the current view`() {
+        val vm = createViewModel()
+
+        vm.selectAll(setOf("search-session-1", "search-session-2"))
+
+        assertEquals(
+            setOf("search-session-1", "search-session-2"),
+            vm.uiState.value.selectedIds,
+        )
+    }
+
+    @Test
+    fun `clean search snippet extracts text from JSON payload`() {
+        assertEquals(
+            "Find the deployment logs",
+            cleanSearchSnippet("{\"role\":\"user\",\"content\":\">>>Find<<< the deployment logs\"}"),
+        )
+    }
+}