style: cut the new rationale comments to one line

AGENTS.md asks for concise non-obvious comments, one line where possible.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/shared/automation-schedules.test.ts

@@ -201,9 +201,7 @@ describe('automation schedules', () => {
   })
 
   it('runs a bare start value with a step through the end of its field', () => {
-    // Why: `5/15` is the shorthand every cron editor and Quartz read as
-    // "from 5, every 15" — 5,20,35,50. Dropping the step silently turned it
-    // into a single value, so the automation ran hourly instead.
+    // Why: `5/15` means 5,20,35,50; dropping the step made the automation hourly.
     const anchor = new Date('2026-05-01T00:00:00').getTime()
     const runs: number[] = []
     let cursor = anchor

src/shared/automation-schedules.ts

@@ -150,10 +150,7 @@ function parseCronField(args: {
       end = parseCronNumber(endPart, args.names ?? null, args.field)
     } else {
       start = parseCronNumber(rangePart, args.names ?? null, args.field)
-      // Why: `5/15` is the shorthand for `5-<max>/15` that Quartz and every cron
-      // editor read as "from 5, every 15". Ending at `start` kept the value and
-      // dropped the step, which no cron dialect does — the automation then ran
-      // once per field cycle instead of on the interval the user wrote.
+      // Why: `5/15` is the `5-<max>/15` shorthand; ending at `start` dropped the step.
       end = stepPart === undefined ? start : args.max
     }