fix: beta numbers for UUID runtime identifiers

[MattKiazyk]

Summary

Fixes simulator runtime beta numbers being incorrectly parsed from UUID-style identifiers.

Apple’s iOS 27 beta 6 runtime uses the identifier:

0218a56d-df74-59c7-a193-7cb21db4a45b

The previous b[0-9]+ expression matched b21 inside the UUID, causing the runtime to appear as iOS 27.0-beta21.

Changes

• Use Apple’s sdkToSeedMappings as the authoritative beta number source.
• Persist the mapped seed number in the downloadable runtime cache.
• Restrict legacy identifier parsing to delimiter-bound components such as _b3_.
• Fall back to the runtime name when older cached data has no seed mapping.
• Document why UUID identifiers must not be searched with an unrestricted beta regex.
• Add regression coverage for UUID identifiers, legacy identifiers, stable runtimes, and cache compatibility.

Testing

• Ran the full XcodesKit test suite.
• 191 tests passed with no failures.
• Built XcodesApp against this branch.
• 35 XcodesApp tests passed with no failures.