Task: Define fast, full, nightly, and release test gates

[RtlZeroMemory]

Parent EPIC: #325

Problem:

The strategy needs a CI shape that matches test fidelity and business risk.

Scope:

• Define what belongs in each gate.
• Make gate boundaries explicit and justified.
• Keep the fast gate small enough for normal PR work.

Done when:

• The repo has a defined gate model for fast, full, nightly, and release coverage.
• The model is detailed enough to drive CI implementation work.

Notes:

• This task should produce work that is reviewable against expected behavior, not current implementation shape.
• Keep outputs straight to the point and tied to repo code or repo process.

[RtlZeroMemory]

Implemented in PR #368: #368

What changed:

• ci.yml now names the fast gate and the full gate explicitly
• new nightly.yml adds the scheduled nightly gate using current real repo commands
• release.yml now repeats the release-critical slices before the release matrix

What was verified:

• workflow content tests passed
• workflow YAML parsed locally
• the release-critical package and terminal slices referenced by the new gates both passed locally

What was intentionally left out:

• no future-only jobs were added
• no dedicated second terminal-real PR job was added beyond the existing full-gate matrix coverage

Remaining ambiguity:

• classification percentage remains out of scope for the repo-side gate model because that source data is not encoded in repo metadata