feat(office-hours): 'never show me these again' for the founder-resources pitch (#538)

The Phase 6 resources offer (34 PG essays + Garry/YC videos) had no
permanent decline — the reporter showed memory instructions kept being
overridden on every update, so people who said no got re-pitched forever.
The offer now closes with a standing choice; opting out runs
gstack-config set founder_resources false (new key, default true, true|false
validated), the write is VERIFIED before any promise (a failed write says so
and skips this session only), and every future session skips the entire
section silently — no resources, no 'skipped as requested' mention. Config
outlives session context, so never means never. Re-enable anytime:
gstack-config set founder_resources true. The pitch stays default-ON for
everyone who never opted out.

Tests pin the key's default/persistence/validation through the real config
bin and the generated section's gate-before-content + write-verify contract.

Approved as a promo-surface change (CEO review D3.4, 2026-08-14).
Ported from time-attack/gstack (GStack 2).

Co-authored-by: Sina Matian <sina@time-attack.dev>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bin/gstack-config

@@ -134,6 +134,7 @@ lookup_default() {
     redact_repo_visibility) echo "" ;; # empty → fall through to gh/glab detection
     redact_prepush_hook) echo "false" ;;
     pair_agent) echo "off" ;; # remote tunnel consent — fail-closed until /pair-agent asks
+    founder_resources) echo "true" ;; # office-hours resource pitch — #538 permanent opt-out sets false
     # Brain-aware planning (v1.48 / T5+T10+T16). Defaults documented inline:
     #   brain_trust_policy@<endpoint-id>  — unset on fresh install; setup-gbrain
     #                                writes 'personal' for local engines,
@@ -315,6 +316,10 @@ case "${1:-}" in
       echo "Warning: pair_agent '$VALUE' not recognized. Valid values: on, off. Using off." >&2
       VALUE="off"
     fi
+    if [ "$KEY" = "founder_resources" ] && [ "$VALUE" != "true" ] && [ "$VALUE" != "false" ]; then
+      echo "Warning: founder_resources '$VALUE' not recognized. Valid values: true, false. Using true." >&2
+      VALUE="true"
+    fi
     if [ "$KEY" = "plan_tune_hooks" ] && [ "$VALUE" != "prompt" ] && [ "$VALUE" != "yes" ] && [ "$VALUE" != "no" ]; then
       echo "Warning: plan_tune_hooks '$VALUE' not recognized. Valid values: prompt, yes, no. Using prompt." >&2
       VALUE="prompt"