feat(skills): operational-readiness-planner for release-readiness pillar

## Skill Name

operational-readiness-planner

## Programming Language

Other — documentation-driven playbook skill (no executable scripts, same as `performance-slo-planner`)

## Purpose

The `release-readiness-gate` skill assesses an **Operational Readiness** pillar (runbooks, rollback, on-call, deploy path), but no dedicated planner produces a consumable artifact — and, unlike Observability, no adjacent support exists at all. The gate assesses this pillar from codebase/ops artifacts only. A standalone, `user-invocable` playbook skill (mirroring `performance-slo-planner`) would give operational readiness the same evidence-backed treatment as the other pillars.

## Prerequisites

None — documentation-driven playbook, no external tools or scripts.

## Requirements

- Standalone `user-invocable` playbook skill (Procedure + Output Format), same shape as `performance-slo-planner`; no phase/state machine or agent.
- Cover runbooks, rollback/backout procedures, on-call + escalation, deploy/release path, and incident-response readiness.
- Write output to `.copilot-tracking/ops-readiness-plans/-ops-readiness-plan.md`; add that folder to the disclaimer / untrusted-content applyTo globs (as done for `release-readiness/`).
- Output maps directly to the gate's "Operational Readiness" pillar so it becomes evidence-backed rather than codebase-inferred.
- Register in the `project-planning` collection (planners live there; the gate consumes cross-collection).
- Update `release-readiness-gate` Default Pillars "Evidence source" to point at this skill.

---

_Context: release-readiness-gate has two pillars without a dedicated producer (Observability, Operational Readiness)._

Start by comparing the proposed skill with `performance-slo-planner` and reviewing `release-readiness-gate`, especially its Operational Readiness pillar and Default Pillars evidence source. Add the standalone user-invocable playbook, register it in the `project-planning` collection, update the disclaimer globs, and write its output to `.copilot-tracking/ops-readiness-plans/-ops-readiness-plan.md`.

Written by the indexing model from the issue text.