skill(signals): inline sync_accounts/sync_governance stubs (remove last cross-reference to seller example)

[bokelley]

Observation

Round-8 signals validator (PR #205) reported:

"Almost no friction. Had to glance at `seller_agent.py` to confirm `governance_agents` shape inside `sync_governance` (url + categories). Skill says 'see examples' but an inline stub would remove the jump. Biggest remaining ask: inline the minimal `sync_accounts`/`sync_governance` bodies (~15 lines total) directly in SKILL.md. That's the last cross-reference in an otherwise self-contained skill."

Round 7 added a "Governance tracks (optional)" section to skills/build-signals-agent/SKILL.md with cross-references to examples/seller_agent.py for full shape. Round 8 confirmed the section unblocks signal_marketplace/governance_denied — time went from 12 min + 3 attempts to 4 min + 1 attempt — but a fresh user still has to jump to the seller example to copy sync_governance shape.

Fix

Inline the minimal sync_accounts + sync_governance bodies directly in skills/build-signals-agent/SKILL.md's Governance section. Copy from examples/seller_agent.py (or the seller skill's own example) — keep both under 25 lines combined. Drop the "see examples/seller_agent.py" cross-reference once inlined.

Priority

4.1 cheap win. Signals skill is ~4 minutes to PASS post-R7 fixes; this makes it fully self-contained.

Related: #205 (round-8 validation)

[bokelley]

Closed by PR #242 — signals skill Governance Tracks section now inlines sync_accounts + sync_governance bodies.