fix(#1627): scale security rigor by ASVS level (planner disposition + auditor depth) (#1636)

workflow.security_asvs_level was display-only — the planner hardcoded
'mitigate if ASVS L1 requires it' and the auditor only echoed the level,
so L2/L3 behaved identically to L1.

- New reference gsd-core/references/security-asvs-levels.md defines L1
  (opportunistic), L2 (standard), L3 (comprehensive) for both planner
  threat disposition and auditor verification depth (higher = superset).
- planner: disposition now scales with the configured ASVS level (no
  hardcoded L1) + @-pointer to the reference.
- auditor: verification depth scales with asvs_level (L1 grep-presence,
  L2 boundary/vector check, L3 end-to-end trace + bypass check).
- planning-config.md + INVENTORY updated; planner kept under its 48K cap
  by extracting the goal-backward worked example to planner-guidance.md.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

gsd-core/references/planning-config.md

@@ -275,7 +275,7 @@ Set via `workflow.*` namespace in config.json (e.g., `"workflow": { "research":
 | `workflow.code_review_depth` | string | `"standard"` | `"light"`, `"standard"`, `"deep"` | Depth level for code review analysis in the ship workflow |
 | `workflow._auto_chain_active` | boolean | `false` | `true`, `false` | Internal: tracks whether autonomous chaining is active |
 | `workflow.security_enforcement` | boolean | `true` | `true`, `false` | Enable threat-model-anchored security verification via `/gsd:secure-phase`. When `false`, security checks are skipped entirely |
-| `workflow.security_asvs_level` | number | `1` | `1`, `2`, `3` | OWASP ASVS verification level. Level 1 = opportunistic, Level 2 = standard, Level 3 = comprehensive |
+| `workflow.security_asvs_level` | number | `1` | `1`, `2`, `3` | OWASP ASVS verification level. Level 1 = opportunistic, Level 2 = standard, Level 3 = comprehensive. Scales both planner threat-disposition rigor (which threats must be mitigated vs. accepted) and auditor verification depth (grep-level → boundary-placement check → full data-flow trace). See `gsd-core/references/security-asvs-levels.md`. |
 | `workflow.security_block_on` | string | `"high"` | `"high"`, `"medium"`, `"low"` | Minimum severity that blocks phase advancement |
 | `workflow.post_planning_gaps` | boolean | `true` | `true`, `false` | Post-planning gap report (#2493). After plans are generated, scans REQUIREMENTS.md and CONTEXT.md `<decisions>` against all PLAN.md files and emits a unified `Source \| Item \| Status` table. Non-blocking. Set to `false` to skip Step 13e of plan-phase. _Alias:_ `post_planning_gaps` is the flat-key form used in `CONFIG_DEFAULTS`; `workflow.post_planning_gaps` is the canonical namespaced form. |