fix: refresh bundled skill safety and workflows

[limityan]

Summary

• refresh the bundled Office skills from pinned Anthropic upstream content and keep BitFun-specific archive handling bounded and cross-platform
• replace the stale embedded agent-browser reference bundle with the pinned dynamic CLI-discovery workflow
• repair gstack browser routing, authentication/cookie flows, local-file handling, and cross-skill references
• add upstream provenance plus regression contracts for embedded content and Office archive safety

Why

The bundled P1 skills had drifted from their upstream sources and contained stale or non-executable references. The Office edit flow also relied on unsafe/non-portable archive commands, while several gstack flows mixed incompatible agent-browser state, cookie, CDP, and authentication semantics.

Scope control

• keeps the same 28 top-level bundled skills; no new skill is introduced
• does not change pdf, writing-skills, or other Superpowers skills
• Office content follows anthropics/skills@fa0fa64; local deviations are limited to bounded archive extraction/repacking, cross-platform invocation, BitFun attribution, the retained 2026 formatting example, and normalized whitespace
• agent-browser follows vercel-labs/agent-browser@81c336c with package 0.32.3; local deviations only preserve BitFun routing, explicit prerequisite handling, and the pinned approved install
• gstack repairs are based on garrytan/gstack@7e96fe2 and the prior BitFun import 6341358; they do not redesign the workflows
• runtime support for additional skill frontmatter and Office helper consolidation are intentionally deferred because they would expand architecture and behavior beyond this maintenance task

Historical customization preservation

• traced all content-changing commits for these bundled skills after their imports, including the Team Mode adaptation in PR docs(agentic): streamline builtin gstack skills and expand team mode prompt #544 and the later xlsx year-example update
• the 866 lines added by the historical docx/gstack customization have 75 exact-line overlaps with this update: 10 BitFun author-attribution lines, 4 old skill references, and 61 pseudo browser/ComputerUse command lines; no overlap remained unclassified
• BitFun author attribution is preserved as one current docx policy, script function/CLI defaults, and a regression contract
• the xlsx 2026 year-format example and agent-browser no-silent-fallback prerequisite policy are preserved with regression contracts
• old skill references are replaced by stable BitFun skill keys
• pseudo browser commands are the only historical Team Mode content intentionally replaced; they now use version-checked agent-browser commands while native desktop UI remains routed to BitFun ComputerUse
• all other Team Mode orchestration, Task ownership, AGENTS.md behavior, .bitfun/team paths, memory, reporting, and review conventions remain on the existing BitFun-customized baseline

Safety and behavior

• agent-browser installation is pinned and requires explicit user approval
• browser-dependent gstack workflows perform one preflight per invocation and stop clearly when the dependency is unavailable
• Office extraction validates every entry before writing and rejects traversal, symlinks, duplicates, file/subpath collisions, excessive entry counts, oversized members/archives, and extreme compression ratios
• local HTML review uses portable temporary paths, file URIs, and explicit file-access permission

Independent review

The complete diff and the historical-customization preservation patch were reviewed adversarially by independent senior-architect and product-design agents. Their findings were fixed and both final re-reviews reported no blocking issues.

Verification

• cargo fmt --all -- --check
• node scripts/check-core-boundaries.mjs
• cargo check -p bitfun-core
• cargo test -p bitfun-core ? 1333 passed, 1 ignored, 0 failed; all integration tests passed
• focused embedded-skill Rust contracts ? 5 passed
• Office archive safety tests ? 3 passed
• Python AST validation ? 43 files
• provenance JSON parse, stale-reference scan, protected-skill scope check, historical-overlap classification, and git diff --check