/nxs.decision-record reads the discovery gists

[sameera]

As a delivery lead, I want /nxs.decision-record to read the marked discovery gists off the epic issue, so that the record is designed on top of the decisions the discovery already settled instead of re-deriving them.

Acceptance Criteria

• Given an epic issue carrying comments with the discovery marker, when /nxs.decision-record runs against that epic, then before it analyses it fetches the epic issue's comments and keeps the ones carrying that marker. Their gists become an authoritative input to the analysis, alongside the epic and its stories.
• Given those gists, then they do not replace the analysis. The command still designs the epic, and it still checks that every story is covered.
• Given a gist that states a decision without its reasoning, then it becomes an open clarification for the human, exactly as an unexplained decision in a design document imported with --from does today.
• Given an epic issue with no marked comment, then the command behaves as it does today, with no new prompt and no empty section.
• Given the marked comments, then the command never edits or removes them.
• Given the full path — graduate a real discovery, promote one of the stubs it produced, then run /nxs.decision-record against the resulting epic — then the record names the decisions the discovery resolved.

Notes

Extends #231, which writes the marked comment. This read is the only change this epic makes to /nxs.decision-record.

A discovery gist and a design document are different things, which is why the gists do not go through the existing --from import mode. Import mode treats its document as the design and replaces the from-scratch analysis with a derivation from it. A gist decides what to build and at what scope. It settles almost nothing about how the epic is built, and it carries no invariants, which is the part of a record the conformance gate later checks against. Feeding gists through import mode would skip the design work on the grounds that the scope work was already done.

Only marked comments are read. An epic issue accumulates ordinary discussion, and feeding all of it to the architect degrades the input. Capturing an out-of-band decision comment in the general case is worth solving on its own terms and is out of scope here.

The failure this story guards against is silent: a read that never runs produces a record that simply does not mention what the discovery decided, and nothing reports the omission. The last acceptance criterion is the walkthrough that catches it, and it is required at the analyze pass.