feat(core-ts): detect() and validate() unit test suites (#189)

[jerrymusaga]

Summary

• Adds packages/core-ts/src/test/detect.test.ts — 20 assertions across 5 describe blocks
• Adds packages/core-ts/src/test/validate.test.ts — 25 assertions across 5 describe blocks
• Both files target the address/detect.ts and address/validate.ts utilities directly, extending beyond the minimal coverage in src/spec/

detect() coverage

Category	Scenarios
Valid addresses	G, M, C — correct kind returned
Case insensitivity	lowercase G, lowercase M, mixed-case G
Corrupted checksums	mutated last char (G), mutated last char (M), interior mutation
Structural failures	empty string, whitespace, numeric, random string, truncated G/M, G with extra chars, all-A string
Wrong-prefix rejection	S-key (secret), T-prefix (unknown), statelessness regression

validate() coverage

Category	Scenarios
No-kind overload	valid G/M/C → true; invalid string/empty → false
Kind-match	G+G, M+M, C+C → true
Kind-mismatch	G+M, G+C, M+G, M+C, C+G, C+M → false
Invalid inputs	corrupted checksum (no kind and with kind), truncated, whitespace, S-key, extra chars
Case insensitivity	lowercase G/M (with and without kind, including mismatch)

Test plan

• CI pnpm --filter stellar-address-kit test passes green
• tsc --noEmit reports zero errors on both files

Closes #189

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[codeZe-us]

@jerrymusaga approved