fix(aidd-pm): spec-template.md has no home for TBD markers, placement is non-deterministic

Read plugins/aidd-pm/skills/04-spec/assets/spec-template.md alongside prd-template.md and references/tbd-marker.md, then inspect assets/spec-validator.yml and the cited build, refine, and SKILL.md text. Done means the affected files consistently designate ## Open Questions as the sole home for TBD markers and state the required zero-before-lock behavior.

Description

04-spec's spec-template.md has no place for unresolved open questions (unlike prd-template.md, which has ## Open Questions). build/refine mark genuine gaps as TBD: <precise question> per references/tbd-marker.md, but with nowhere designated to put them, placement is left to the drafting agent's judgment each run — confirmed non-deterministic by two real runs on the same project: one run put 3 TBDs in ## Hard constraints (where they read as nonsense — a hard constraint can't be undecided, and it contradicts spec-validator.yml's own definition of that section: "concrete and testable, not vague"), a later run on a refined version of the same feature put the same kind of TBDs under ## Context instead.

Expected behaviour

spec-template.md gets a ## Open Questions section (mirroring prd-template.md). Every TBD: — regardless of which section it would eventually fill — lists there, once, deterministically. Target, Hard constraints, Non-goals, and Done-when stay 100% resolved, concrete content only; incomplete because a decision is pending is fine, but nothing vague sits inside them. spec-validator.yml and the citing text in 01-build.md/02-refine.md/SKILL.md's Transversal rules need the matching update (TBD's home becomes ## Open Questions, not "wherever the missing field lives").

Note: unlike PRD's Open Questions (which can legitimately persist post-completion — deferred, non-blocking items), a spec's Open Questions should drive to zero before the spec validates/locks (spec-validator.yml's any_required_unfulfilled: invalid already enforces this for required sections) — worth stating explicitly so the section doesn't silently become a place TBDs go to be forgotten.

Affected file(s)

plugins/aidd-pm/skills/04-spec/assets/spec-template.md, assets/spec-validator.yml, actions/01-build.md, actions/02-refine.md, SKILL.md

Observed behaviour

Same feature, two separate 04-spec runs, two different TBD placements (Hard constraints vs Context) — no section owns it, so the drafting agent improvises each time.

AI tool

Claude Code

OS

macOS

Additional context

Surfaced during #564's router-contract migration (out of scope there — behaviour change, that issue is shape-only). Related to #625 (SDLC never checks spec-validator.yml before treating a spec as a finished contract) but a different root cause: this is the template itself having no home for the marker, not the orchestration layer failing to gate on it.