[followup] Machine-readable stability tier per component

[trilamsr]

Source: docs/followups/opportunistic.md row 2 (Next up).

Today stability is declared in two places (per-component README header + CHANGELOG entry). When tracecore components (a future CLI subcommand listing built-in components) or a policy/required-alpha-warn-banner lint check exists, extend components.yaml with a stability: field per entry and have tools/components-gen emit it.

Files to touch:

• components.yaml — add stability: field per entry.
• tools/components-gen/main.go — emit the field.

Trigger: first machine reader of stability data (e.g., the tracecore components CLI subcommand, or a lint check that requires alpha-banner presence based on machine-readable tier).

Acceptance:

• components.yaml has stability: alpha|beta|stable per component, matching the README header today.
• tools/components-gen round-trip keeps the field.
• A consumer (CLI subcommand or lint check) reads the field — don't add the field with no reader.

[trilamsr]

Outdated by RFC-0013 distribution-first pivot (docs/rfcs/0013-distro-first-pivot.md §7). The referenced receiver/scaffold is deleted in v0.1.0/v0.2.0; this followup no longer applies.