FIX: Small code-review fixes + FAQ section

[kishorereddy]

Overview

1. Code review cleanup: four small correctness/design fixes from a code review pass.
2. New FAQ section: added to the README, covering design rationale and common questions.

Ticket(s)

N/A

Link(s)

N/A

Example(s)

// Rejected requests now map to a client-side HTTP code, not a server-fault one
CodesToHttp().toCode(Rejected.RULE_VIOLATION) // 409, was 500

// Override maps now match by identity (origin+name), not full field equality
val differentMessage = Failed.Invalid("NOT_FOUND", "a different message", origin = "kiit")
CodesToHttp().toCode(differentMessage) // still resolves to 404

Dependencies

None.

Design

1. Removed copyAll: Status no longer exposes a general-purpose copy method. Its one real
   dependent, Status.ofStatus, still works the same way internally, just without a public mutation
   escape hatch.
2. Removed isNeutral: a computed convenience that read as contradictory in practice
   (Excluded being both success = true and "neutral" at once). is Passed.Excluded || is Passed.Information is still trivially available inline.
3. Fixed Rejected's HTTP default: 500 → 409: a well-formed, understood request that's
   refused on a business rule is a client-side outcome, not a server fault.
4. Override maps now key on identity, not full equality: Status is a data class, so the old
   Map<Status, Int> overrides compared every field, including the message. Two statuses with the
   same identity but a slightly different message could silently miss their override. Rekeyed to
   match on origin + name instead.
5. Confirmed gRPC UNSUPPORTED → 12: previously flagged as an inference; now confirmed and
   documented as such.
6. New FAQ section in the README covering design philosophy, comparisons to alternatives
   (Arrow, kotlin-result), taxonomy details, adoption guidance, and maturity/trust questions.

Notes

None.

Pending

None.

Tests

1. Updated tests for the HTTP default change (409 instead of 500) and the resulting shift in which
   codes tie at 409 vs 500.
2. Added regression tests confirming override maps and CompositeLookup match by identity even
   when the message differs.
3. Removed tests that only existed to exercise copyAll/isNeutral directly.
4. Full ktlintCheck + detekt + jvmTest + jsNodeTest run clean.