Documentation: issue-494

Capability docs

• docs/capabilities/spec-workflow.md: the gate rule, the brainstorm EARS line, and a History row for issue-494.
• docs/capabilities/process-graph.md: the absentOutcome / gate / whenPresent rule and its fail-closed behaviour (with HookContext.visited), what --recompute reports for a present brainstorm, the lock-artifacts note, and a History row.

Documentation

Files updated to describe brainstorm-approval:

• skills/the-loop/SKILL.md: the chain intro, artifact 0, and the Gate-less artifacts rule (now tasks.md only)
• skills/the-loop/reference/workflow.md: the approval-node list, the locking list, Phase 0, Brainstorming is optional
• skills/the-loop/templates/brainstorm.md: front-matter comments and the header note
• commands/brainstorm.md, commands/work-on.md, commands/new-requirement.md: the gate, and the declared-skip and pre-ticket cases for an unlocked brainstorm
• docs/capabilities/spec-workflow.md: the gate rule, the brainstorm EARS line, a History row
• docs/capabilities/process-graph.md: the absentOutcome / gate / whenPresent rule, the lock-artifacts note, a History row
• README.md: the gate-less sentence

T9 check: grep -rn "no approval gate\|no gate approves a brainstorm\|gate-less\|advances on shape alone\|advance on shape alone" skills commands docs/capabilities README.md rules | grep -i brainstorm returns only the new wording and the issue-281 History row, which records what was true then.