chore(maintenance): align CI matrices and repository templates

[dreamorosi]

Summary

Align CI package coverage, issue metadata, and the RFC discussion form with the repository's current packages and organization configuration.

Changes

• add every publishable package to the PR and merge-queue CI matrices
• document the intentional exclusion of the private packages/testing workspace
• replace archived issue labels with the available Bug, Enhancement, and Task Issue Types
• update stale issue links to avoid archived labels and use Issue Type search syntax
• rename the RFC form to match its category slug and add missing utility areas
• correct stale PR-requirement and RFC links
• keep the package matrices explicit; deriving them dynamically from workspace metadata remains follow-up work
• note that RFC form rendering can only be verified after merge by opening a draft RFC discussion

Note: draft while dedicated organization Issue Types are being created — the issue-form type: mappings will be updated once they exist. Also overlaps with #5618 (deletes docs/roadmap.md, rewrites CONTRIBUTING.md) and #5634 (same workflow files); will be rebased after those merge.

Issue number: closes #5631

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