docs(skills): seller-skill behavioral coverage gaps — 5 patterns from matrix v4 (#1120)

[bokelley]

Closes #1120

Docs-only changes to skills/build-seller-agent/SKILL.md and skills/build-seller-agent/specialisms/sales-guaranteed.md. No changeset needed — skills/ markdown is excluded from the changeset requirement per CLAUDE.md.

Matrix v4 surfaced 5 behavioral patterns where LLM-built sales_guaranteed agents failed storyboard scenarios despite framework-correct scaffolding. This PR adds the missing teaching signal in the skill files:

• Pattern 1 (sync_accounts omitted): Added a sales-guaranteed minimum-tool-surface callout immediately after the tools table. The required surface is 10 tools (note: list_creatives is optional — only required if the seller hosts its own creative library; omitted from the mandatory list per SalesPlatform interface classification).
• Patterns 2+5 (TERMS_REJECTED, PACKAGE_NOT_FOUND missing): Added an error-code matrix covering all spec-defined rejections on create_media_buy and update_media_buy. Fixed a contradictory comment at the old line 523 that said "not adcpError" when adcpError is the correct mechanism throughout.
• Pattern 3 (pending_creatives never exits): Rewrote the updateMediaBuy example to advance pending_creatives → pending_start (future start_time) or active (past/now) when creative_assignments arrive. Added key-point Fix Fly.io deployment host/port configuration and add regression tests #8 to the key-points list.
• Pattern 4 (property_list/collection_list field path wrong): Fixed sales-guaranteed.md's example from pkg.property_list (no such field on PackageRequest) to pkg.targeting_overlay (correct per generated types — TargetingOverlay contains property_list/collection_list; neither Package nor PackageRequest has them as direct fields). Added a storyboard-discrepancy note: the inventory_list_targeting grader may check packages[].property_list (flat) rather than the spec-correct packages[].targeting_overlay.property_list; the upstream storyboard fix belongs at adcontextprotocol/adcp.

Nits surfaced (not fixed — see pre-PR review):

• The minimum-tool callout is partly redundant with the table above it; kept for LLM-scanning salience.
• The storyboard-discrepancy note's exact grader path is unconfirmed against the storyboard YAML; "may check" hedging added.

What was tested

• npm run format:check — ✅ all files pass Prettier
• npm run typecheck — pre-existing TS2688/TS5107 errors on main confirmed prior to this branch; no new errors introduced
• npx tsx scripts/typecheck-skill-examples.ts — ✅ no new errors (229 known baselined, 33 blocks compiled)
• Pre-push validation hook — ✅ passed (~6s)

Pre-PR review

• code-reviewer: approved — paused-guard fix correct (patch.paused === false), list_creatives removal correct per SalesPlatform interface, BUDGET_TOO_LOW addition correct, storyboard-path nit addressed in note
• ad-tech-protocol-expert: approved — TERMS_REJECTED bundling of measurement_terms+performance_standards confirmed in docs/llms.txt line 913; BUDGET_TOO_LOW vs INVALID_REQUEST distinction confirmed per error taxonomy; targeting_overlay.property_list nesting confirmed in generated types; pending_creatives trigger via update_media_buy aligns with storyboard flow at docs/llms.txt line 916–917

Triage-managed PR. This bot does not currently iterate on
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issue). To unblock:

• Push fixup commits directly: gh pr checkout <num> →
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See adcp#3121
for context.

Session: https://claude.ai/code/session_01LYWfxv9GxrAwXKYVZ1cXGJ

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