ci(docs): dispatch convoy-go, convoy.rb and convoy-php SDK generation

[mekilis]

Summary

• Adds convoy-go, convoy.rb, and convoy-php to the SDK regeneration dispatch matrix. Each repo owns its generator behind the shared sdk_generation.yaml filename and inputs (convoy-go: oapi-codegen; convoy.rb / convoy-php: OpenAPI Generator), so the dispatcher contract is unchanged.
• Updates the header comment: SDK_REPOS_PAT must be able to dispatch workflows and open PRs on all six SDK repos.

Companion PRs adding the pipelines: frain-dev/convoy-go#60, frain-dev/convoy.rb#20, frain-dev/convoy-php#11.

Test plan

• After the three SDK repo PRs merge and SDK_REPOS_PAT covers the new repos, a dispatcher run should fan out to all six repos (no-diff repos skip PR creation).

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Note

Low Risk
Docs and CI matrix only; no runtime code. Operational risk is ensuring SDK_REPOS_PAT permissions include the three new repos before the next dispatch.

Overview
Extends the OpenAPI → SDK regeneration dispatcher so speakeasy-sdk.yml fans out to six language repos instead of three, adding convoy-go, convoy.rb, and convoy-php to the trigger-sdk-repos matrix. Each new repo is expected to implement the same sdk_generation.yaml contract (force, feature_branch); generators are documented as oapi-codegen for Go and OpenAPI Generator for Ruby/PHP.

SPEAKEASY_SDK.md is updated to match: generator/scope tables, pipeline diagram, and secret guidance now state that SDK_REPOS_PAT / SDK_BOT_PAT must cover all matrix repos. The note deferring Go/Ruby/PHP codegen is removed.

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