Thin the app's comments

The same pass the server had, on the Kotlin side: comments restating what
the code says are gone, and the ones recording a measurement, a constraint
or an incident are kept but cut to a few lines each. 6540 comment lines to
5674, and 920 lines off the app.

Two doc comments had drifted onto the item above the one they describe --
`contextAfter`'s onto `sessionWorking` in Events.kt, and `UsageMonitor`'s
equivalent on the server was fixed in the previous commit. Each is back on
its own item, which is the only non-comment line this diff moves.

The comments are reflowed to the column limit at their own indentation:
several were written wide, and ktfmt re-wrapped them into lines holding a
single orphan word. `/tmp` script, not kept -- ktfmt is idempotent over the
result, which is the check.

Left alone deliberately: this codebase's remaining comment density is high
because the comments carry things the code cannot say -- what a null means,
what a number was measured against, which bug a guard exists for. Of the
238 one-line doc comments in the app, five were pure restatement of the
name and were removed; the rest each say something the signature does not.

ktfmtFormat, compileDebugKotlin, lintDebug and testDebugUnitTest pass;
cargo test (127), clippy --all-targets and fmt still clean.

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

app/androidApp/src/main/kotlin/com/example/aiapp/Durations.kt

@@ -5,13 +5,12 @@ package com.example.aiapp
  *
  * A tool's timeout arrives as `480000`, which nobody reads as eight minutes. The rule has two
  * halves, because a short span and a long one are read for different things. Under a minute the
- * question is "roughly how long", so only the largest unit is shown and a fraction of it carries
- * the rest -- `2.5s`, `30ms`. At a minute or more the question is "how long exactly", so every unit
- * that has something in it is written out -- `5d 12h 4m`. Units that are empty are left out rather
- * than written as zero, since the labels say which is which and `5d 0h 4m` is only longer.
+ * question is "roughly how long", so only the largest unit is shown and a fraction carries the rest
+ * -- `2.5s`. At a minute or more the question is "how long exactly", so every unit with something
+ * in it is written out -- `5d 12h 4m`. Empty units are left out rather than written as zero.
  *
  * Sub-second precision is dropped past a minute: nothing that takes days is measured in
- * milliseconds, and carrying them would make the common case the widest one.
+ * milliseconds.
  */
 fun formatMillis(ms: Long): String {
     if (ms < 0) return "-" + formatMillis(-ms)