feat(perps): add write-perps-ticket product-authoring skill

[abretonc7s]

What

Adds write-perps-ticket — the product (first) pass that pairs with breakdown-perps-tickets (#57, the engineering pass). It helps a PM (or a Claude acting for one) turn a raw observation/idea/goal into one clean, complete ticket that states intent and expected outcome, then stops before implementation.

Splits the two jobs the team actually has (per the product discussion): the PM describes what's broken / expected with no implementation, and engineering does the technical split + layer routing as a second pass.

Modes

Typed, each with its own tight format:

• Bug — what's broken + testable expected + repro + surface + pre-conditions + severity
• EPIC — user-facing outcome + feature-level acceptance + scope (tasks deferred to engineering)
• Initiative — why + measurable success metric + scope boundary + candidate child EPICs

Why these choices

• Intent, not implementation. Product tickets state testable outcomes — no file paths, component names, or layer routing. Prescribing implementation boxes engineering in and goes stale when code moves; routing needs codebase access and belongs to the breakdown pass.
• Surfacing section (severity, plain-words area label, correct type) so reported bugs get triaged instead of lost in the backlog — a direct pain point.
• Number semantics, not decimals. Expected values described semantically ("shows USD value") since perps precision is range-adaptive.
• Clean handoff. Output of this skill = input to breakdown-perps-tickets. Both reuse domains/perps/knowledge/*.

Relation to #57

Complementary, not dependent. #57 = engineer split/route; this = PM authoring. Merge order doesn't matter.