FIX: Reword Excluded.OMITTED and add taxonomy sample walkthroughs

[kishorereddy]

Overview

Small wording fix to Excluded.OMITTED's message, plus new sample code that walks through
picking the right status for common validation scenarios.

Ticket(s)

N/A

Links(s)

N/A

Example(s)

• test2() in the sample app randomly builds one of the 8 status groups and prints both the
  group name and the specific status name, a quick way to see the whole taxonomy in one run.
• test3()/validatePhone(...) shows a realistic validation function that picks a different
  status group depending on why the input failed: bad format (Invalid), a reserved test value
  (Rejected), or a caller-restricted number range (Restricted).

Dependencies

None.

Design

1. Wording fix: Excluded.OMITTED's message changed from "The item was left out." to "The
   item was excluded from the result.", clearer and more consistent with the other Excluded
   members' phrasing. OMITTED stays the first-declared, default member of the group.
2. Sample app: added test2() and test3() to sample-kotlin's SampleApp.kt, demonstrating
   building/matching all 8 status groups and a small validatePhone function that shows how to
   pick between Invalid, Rejected, and Restricted depending on the failure reason. The
   original test1() demo (unchanged) is temporarily commented out of main() while iterating
   on the new examples.

Notes

validatePhone's Restricted case is keyed off an explicit caller parameter (defaults to
"guest"), since Restricted is about who's asking, not what value they passed in, an earlier
draft used Restricted for a value-based rule, which didn't quite fit; this version ties it to
an actual identity/permission check instead.

Pending

n/a

Tests

No unit tests added, this is sample/demo code. Verified via ./gradlew :kiit-codes:jvmTest and
:samples:sample-kotlin:compileKotlin, both pass.