fix(cli): decode JSON Pointer escape sequences in AsyncAPI V3 parser

[fern-support]

Description

Refs: Investigation for Smallest AI websocket generation issue

Fixes the AsyncAPI V3 parser to properly decode JSON Pointer escape sequences in channel references per RFC 6901.

When AsyncAPI specs have channel paths containing slashes (e.g., /api/v1/ws), these are encoded as ~1 in JSON Pointer $ref values (e.g., #/channels/~1api~1v1~1ws). The parser was not decoding these escape sequences, causing channel lookups to fail and AsyncAPI documents to be skipped during parsing.

Changes Made

• Added JSON Pointer escape sequence decoding (~1 → /, ~0 → ~) in getChannelPathFromOperation()
• Rewrote message reference resolution in AsyncAPIV3ParserContext.resolveMessageReference() to properly extract and decode channel paths before lookup
• Added defensive null check for operation.channel with descriptive error message
• Added changelog entry for version 3.60.2

Testing

• Manual testing with minimal AsyncAPI V3 fixture containing URL-encoded channel paths
• Verified websocket client code is generated correctly after fix
• Lint checks pass (pnpm run check)
• Seed test fixture not added (consider adding for regression prevention)

Human Review Checklist

• Verify escape sequence decoding order is correct (~1 before ~0 matters per RFC 6901)
• Consider whether a seed test fixture should be added for AsyncAPI specs with encoded channel paths

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Link to Devin run: https://app.devin.ai/sessions/6edd55620e9c49c2a7edd190fe1e16d7
Requested by: @fern-support

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