Bump emitter version to 0.54.0

[Copilot]

Monthly minor version bump for June 2026.

Package	Old	New
@azure-tools/typespec-ts	0.53.3	0.54.0
@azure-tools/rlc-common	0.53.3	0.54.0
@autorest/typescript	6.0.73	6.0.74

Changes since 0.53.3

• [Feature] Bump TypeSpec dependencies to latest stable and next pre-release versions. #4012
• [Feature] Remove head-as-boolean emitter flag (superseded by TCGC @responseAsBool). #3986
• [Feature] Decouple typespec-ts from rlc-common. #3926
• [Feature] Improve resolveReferences performance. #4004
• [Feature] Update naming terminology: cadl-ranch → spector, HLC → AutoRest. #3957
• [Feature] Bump turbo from 2.6.3 to 2.9.14. #3989
• [Bugfix] Fix config/script gaps between JS emitter and SDK libraries. #4006
• [Bugfix] Fix deserializer throwing on empty response body (success and error paths). #3948