flow-inventory-addlisted

# flow-inventory-add Append-only sub-skill that adds one row OR one section to `docs/product/master-flow-inventory.md`. Two modes are dispatched by the calling orchestrator; this skill is the shared inventory-write layer that `/flow:add-sub-flow` and `/flow:add-domain` call into. This skill is **NOT user-invocable** (`disable-model-invocation: true`, per Q7). **Append-only contract.** Existing rows are never rewritten. Existing IDs are never renamed (CLAUDE.md "never rename existing IDs" guardrail + master-flow-inventory.md schema lock). Silent overwrites are not a v1 behaviour — duplicate IDs hard-reject. The full design rationale lives in `docs/design-rationale/fda-plugin-interview.md` Q20 (memory:224-238). Q19 (memory:208-222) defines the parent 5-phase greenfield interview. `domain-add` mode invokes the Q19-mini subset — Phases 1+4+5, scoped to one domain — sourced from two layers: | Phase | Sourced from | Content | |---|---|---| | 1 (base classifier) | `_shared/app-classifier-pattern.md` | framework / app category / persona shape / scale | | 1 (greenfield follow-ups) | `flow-inventory-interview/SKILL.md` body, Section 2 | the 4 Q19.2 follow-up questions (domain envisioning, density, MVP sequencing, persona density) | | 4 (synthesis) | `flow-inventory-interview/SKILL.md` body, Section 3 | 3-tag scope-priority taxonomy, but scoped to one domain | | 5 (user confirmation) | `_shared/app-classifier-pattern.md` | preview rendering + Approve/Edit/Reject | `_shared/app-cla