Accept Edict Target IR obstruction fixture and emit Echo receipt

[flyingrobots]

Goal

Add the first Echo-side runtime bridge for Edict-produced echo.span-ir/v1 Target IR by accepting a narrow fixture and emitting deterministic attempt outcome evidence for a pre-step obstruction requirement.

This is the Echo half of the obstruction-strand corridor after Edict PR #132. Edict now emits canonical Target IR requirements with terminal and continueObstructed dispositions; Echo should consume that shape without claiming full Edict admission, scheduler counterfactuals, Jim completion, or general plugin dispatch.

Acceptance criteria

• Echo has a checked-in fixture or test-owned fixture that represents Edict-produced echo.span-ir/v1 Target IR with a pre-step continueObstructed requirement.
• Echo accepts the supported fixture shape and rejects wrong-domain, missing-requirement, unsupported-disposition, and malformed-digest variants with stable structured errors.
• Echo evaluates one pre-step requirement against deterministic in-memory inputs.
• Echo emits a deterministic receipt/result with an explicit attempt outcome such as obstructed_attempt for stale-basis-style obstruction.
• The receipt/result binds the Target IR artifact digest supplied by the fixture.
• A fresh/satisfied requirement path remains distinct from an obstructed attempt if included in scope.
• Tests distinguish:
  • accepted artifact versus executed receipt;
  • obstructed attempt versus invalid proposal;
  • obstruction versus legal unselected counterfactual.
• Documentation and changelog state that this is a narrow Echo fixture bridge only.

Non-goals

• No general Edict bundle admission.
• No participant policy engine.
• No Jim product operation set.
• No XYPH Quest settlement.
• No scheduler counterfactual explorer.
• No canonical Echo receipt bytes unless this PR explicitly freezes an encoding.
• No general target plugin registry.

References

• Supports Echo 1.0: Edict Native Invocation in Echo #583.
• Supports Gate C - Native Jedit-on-Edict Execution #589.
• Supports Supported Outcome Settlement: attempt outcome vocabulary for Jim Evidence Gate #640.
• Follows Edict PR Echo/how does echo work book #132 and Edict issue F32 scalar/canonicalize zero #131.

[coderabbitai]

🔗 Related PRs

#145 - AIΩN bridge doc + tick receipts (#144) [merged]
#329 - Stack Witness 0001 fixture-backed jedit walking skeleton [merged]
#344 - feat(wesley): consume canonical requirements artifacts [merged]
#354 - feat(core): add runtime support v0 boundary [merged]
#358 - feat(core): add admission evidence boundaries [merged]

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