feature-ideation reusable calls the model but ignores AGENTS_PAUSED, so a fleet pause does not stop it #1295

Problem

AGENTS_PAUSED=true is the switch that pauses the agent fleet. In petry-projects/.github-private every model-calling workflow now honours it or is listed as exempt (see "AGENTS_PAUSED stops only dev-lead", petry-projects/.github-private #2249). One path could not be fixed there because its logic lives here:

.github/workflows/feature-ideation-reusable.yml calls the model (the Claude action) and never reads the variable. Its callers are frozen stubs in the consumer repositories, so the gate has to be in the reusable.

Scope

1. In feature-ideation-reusable.yml, skip the model-calling job when vars.AGENTS_PAUSED == 'true' (read in the calling repository's context, so an organisation-level variable pauses every consumer), in the same way dev-lead-reusable.yml does in .github-private.
2. Make the skip visible: one notice naming the pause source (vars.AGENTS_PAUSE_SOURCE) and until time (vars.AGENTS_PAUSE_UNTIL) when present.
3. Check the other reusable workflows in this repository for a model call that does not honour the variable, and list the result in the PR. A read-only check on 2026-10-11 found none besides this one at the refs .github-private pins, but it covered only those refs.

Acceptance criteria

1. A test that the model-calling job is skipped when the variable is true and runs when it is unset or false.
2. No change in behaviour when the variable is unset. No edit to the caller stub template.
3. The PR states which channel tag has to move before consumers get the gate.