Clean up the app: one fix per rule already written down somewhere else

A pass over every Kotlin file, fixing each place a rule the codebase had
already learned was applied to only one member of its set:

- Notifications: checkSelfPermission(POST_NOTIFICATIONS) on Android 12 and
  below answers "denied" for a permission that does not exist there, so
  every notification on API 24-32 was silently dropped. Version-guarded;
  before 13 the app-level switch is the whole answer.
- The permission-mode list was written three times and had drifted: the
  import screen was missing "plan". One list in Api.kt now.
- The import screen's delete refetched the whole list through a loading
  spinner -- the exact fault the session list's delete already fixed and
  documented. It now removes only the deleted row.
- The import screen truncated paths at a hardcoded 40 characters; it now
  uses StartEllipsis against the row's real width, like the models screen.
- warm() bypassed the partsOf cache built for it, re-scanning every loaded
  message per page, and warmed a multi-block memory note under keys no row
  looks up. It now mirrors transcriptUnits through the same caches.
- The transcript's data model (TranscriptItem, foldEvent, joinPages, warm)
  moved out of SessionScreen.kt into TranscriptItems.kt: pure folding with
  no screen in it, changing for unrelated reasons in the same file.
- One image fetch/decode/failed block was written twice; it is
  rememberSessionBitmap in SessionImage.kt now.
- Lint is fully clean: android.media.ExifInterface replaced with the
  androidx one (the framework copy lacks the hostile-image parsing fixes,
  and these images arrive from outside the phone), highlights bumped to
  1.1.0, and the notification fix above closed InlinedApi.
- Dead weight out: an unused act() onFailure parameter, and five orphaned
  or misattached doc comments (UserBubble carried SessionImage's doc).

Verified: ktfmt, compileDebugKotlin, lintDebug (0 issues), server suite
(93 passed), clippy and rustfmt clean; exercised on the emulator against a
real imported transcript -- paging, tool groups, block rendering, no
crashes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/androidApp/build.gradle.kts

@@ -146,4 +146,5 @@ dependencies {
     implementation(libs.zxing.embedded)
     implementation(libs.markdown.renderer)
     implementation(libs.highlights)
+    implementation(libs.androidx.exifinterface)
 }