feat(decisioning): advance validate_platform() enforcement of required sales-* methods

[bokelley]

Context

The Protocol docstring at src/adcp/decisioning/specialisms/sales.py:184-227 says 9 methods are required for sales-* specialisms, but validate_platform() only enforces this in v6.0 rc.1. The v3 ref seller would have shipped with 4 missing methods without manual catch in deep review.

Either advance enforcement now OR surface a one-time UserWarning per missing method until adopters opt in.

Acceptance Criteria

• validate_platform() either errors or emits a one-time UserWarning per missing required sales-* method
• Docstring at src/adcp/decisioning/specialisms/sales.py:184-227 updated to reflect current enforcement timeline
• Adopter-visible: missing methods are surfaced before runtime

Files

• src/adcp/decisioning/specialisms/sales.py:184-227

[bokelley]

Triage

Classification: Bug (correctness gap — docstring declared required, framework silently tolerated absence)
Bucket(s): handlers
Status: drafting-pr
Milestone: omitted (no target version named in issue)

What the experts said:

• code-reviewer: approved — no blockers; stale inline comment in REQUIRED_METHODS_PER_SPECIALISM flagged and fixed
• dx-expert: two blockers resolved before PR opened — sync_catalogs miscategorized under warn-if-absent section, # ---- Optional ---- inline comment not updated (both now fixed); nits on __qualname__ in message and __all__ (also fixed)

My take: UserWarning at boot is the right non-breaking path for v6.0 alpha → rc.1 promotion. The fix adds WARN_IF_MISSING_PER_SPECIALISM, a new warning loop in validate_platform() (deduplicated across multi-specialism claims), and updates the SalesPlatform docstrings to match reality. Draft PR #434 covers all three acceptance criteria.

Drafting PR: adds WARN_IF_MISSING_PER_SPECIALISM + warning loop in validate_platform() + docstring corrections; 4 new tests (42 passing).

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Triaged by Claude Code. Session: https://claude.ai/code/session_01GovN4hXXs27SNeNbBeFRgg

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