refactor(hephaestus): tighten GPT-5.5 prompt for outcome-first density

Compress 6 discovery sections into one Discovery & Retrieval section, remove three-way echo of "drive the artifact" between Goal, Manual QA Gate, and Forbidden stops (now once + cross-ref), split persona prose into Tone vs Autonomy & Collaboration per OpenAI's GPT-5.5 prompting guide, trim Output formatting from 13 prior-restating bullets to 5 environment-specific ones, and defer the Oracle wait policy to the dynamic oracleSection so it lives in a single source of truth.

Add buildFrontendGuidanceSection: conditional injection that only emits the anti-slop frontend block when `visual-engineering` category is unavailable, since the category-skills guide already forces visual work to delegate when the category exists.

Static prose drops 277 -> ~175 lines (-37%); every Hephaestus identity item preserved (Manual QA Gate surface map, Intent table + commitment line, three-attempt failure protocol, Hard invariants, no defensive code, AGENTS.md and dirty worktree handling, four dynamic placeholders).

src/agents/dynamic-agent-prompt-builder.ts

@@ -15,6 +15,7 @@ export {
   buildLibrarianSection,
   buildDelegationTable,
   buildOracleSection,
+  buildFrontendGuidanceSection,
   buildNonClaudePlannerSection,
   buildParallelDelegationSection,
 } from "./dynamic-agent-core-sections"