Model Agent Run identity in task inventory

[schickling]

Problem

st2 exposes stable Agent Spec identity, resolved task runtime ID, backend runtime generation, and the desired/observed launch generation tracked in #40. It does not expose a provider-neutral Agent Run ID for one concrete successful launch occurrence.

A backend generation, PID, PTY ID, declaration identity, or provider-native transcript ID is not an Agent Run ID. Collapsing them prevents downstream inventory and telemetry from distinguishing adoption of one run from a later relaunch of the same task.

Logical Agent Session identity is owned by Axe and its harness drivers under #124. st2 may carry that independently supplied opaque correlation value, but it must not allocate it or infer session continuity.

Contract

Add a typed provider-neutral execution envelope:

agentSessionId  optional opaque value supplied by the compiled launch contract
agentRunId      minted by st2 exactly once for each successful launch occurrence

Recommended durable IDs follow the registered ARN-style resource-name contract:

arn:agent:<stable-scope>:session:<collision-resistant-id>
arn:agent:<stable-scope>:run:<collision-resistant-id>

This issue owns Agent Run allocation and inventory propagation. #124 owns Agent Session allocation, provider-native identity, and session semantics.

Required behavior

• Mint one Agent Run ID for a successful fresh launch or relaunch.
• Do not mint a successful run identity for a launch that fails before the task exists.
• Inspection and reconciliation preserve the same Run ID for the same live run.
• Adoption preserves independently persisted Run and Session evidence or reports each as unknown; it never fabricates continuity.
• A later successful recreation keeps a supplied Agent Session ID when the compiled contract keeps it and always changes the Agent Run ID.
• Propagate the envelope consistently to PTY/exec runtime metadata, child launch context, and machine-readable task inventory.
• Keep both values descriptive correlation metadata. They grant no lifecycle or authorization capability.
• Never alias either value to backend generation, desired/observed launch generation, task ID, or provider-native transcript identity.

Acceptance

• One running execution keeps the same Run ID across inspection and adoption.
• A successful relaunch changes the Run ID exactly once.
• A failed launch does not publish a successful Run ID.
• A supplied Session ID survives a resume/re-execution while the Run ID changes.
• A new logical session supplied by Axe changes both values.
• Legacy adoption without evidence reports unknown rather than minting history.
• PTY and exec backends expose equivalent envelope semantics.
• Declaration identity, runtime ID, backend generation, launch generation, Session ID, and Run ID remain pairwise distinguishable in fixtures.

Dependencies and scope

• Define renderer-owned harness sessions and the generic st2 lifecycle boundary #124 owns logical session allocation and renderer/harness behavior.
• Expose desired versus observed launch generation for adopted tasks #40 owns the effective launch-contract generation.
• Add an exact generation-fenced recreate operation for one live task #110 consumes runtime and desired-generation fences for explicit recreation.
• Epic: stable agent identity and mutable presentation metadata #128 owns stable Agent Spec automation identity versus mutable presentation.

This issue does not define transcript stores, provider flags, fresh/resume selection, or another launch-contract hash.