Pi intercom runtime capability probe

[clkao]

Pi intercom supervisor talkback now has a reusable runtime capability probe with durable evidence. The probe distinguishes setup checks from behavioral child-to-supervisor communication proof.

What changed

• Added Pi intercom capability probe recipe
• Added schema-tested not-run and passed evidence records
• Validated child progress, decision, reply, resume, and marker behavior

Evidence

• 3/3 validation suites passed after rebase
• Live probe verified progress/decision/reply/resume/marker chain

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cq

[clkao]

Closing as superseded by the spike reframe and follow-up product work in #304/#305. The Pi intercom talkback probe remains recorded as spike evidence in workflow state; this PR is not a product implementation to merge.