decisioning: align hello_seller.py with validate_platform soft-warn surface

[bokelley]

From the salesagent v3.12 → 4.x migration (SDK_FEEDBACK.md, item #9).

hello_seller.py implements 5 methods. Running validate_platform against it warns about 4 additional missing methods that are "required by the SalesPlatform Protocol for any sales-* specialism in v6.0 rc.1+":

• get_media_buys
• list_creative_formats
• list_creatives
• provide_performance_feedback

Adopter quote:

The canonical minimal example trips the soft-warn. Either the example should implement them, or the warning's threshold is wrong.

Decision needed

Pick one:

• Expand the example. Update hello_seller.py to implement the 9-method minimum surface. Forces adopters to see the full required shape from the start.
• Relax the warn threshold. Decide which subset is genuinely required for sales-non-guaranteed and only soft-warn on those. Keep hello_seller.py minimal as the on-ramp.

The signal-mismatch is the bug. Code change scoped to examples/hello_seller.py OR src/adcp/decisioning/specialisms/sales.py depending on the call.

[bokelley]

Triage

Classification: Bug (signal-mismatch between canonical example and validator)
Bucket(s): examples
Status: drafting-pr
Milestone: omitted (no target version named in issue)

What the experts said:

• dx-expert: don't relax the threshold — the warning exists because the v3 ref seller shipped missing four spec-required methods by accident; removing the fence repeats that failure. Expand the example with clearly-annotated stubs.
• docs-expert: a canonical "hello world" that emits warnings at boot teaches adopters to ignore validator signal; option 1 (expand) is recommended; module docstring needed updating regardless.
• code-reviewer (pre-PR): approved after fixes — stale "3 implemented" count corrected, D1 projection signatures verified correct, dispatch-path test coverage added for all four new stubs.

My take: The four methods are in RECOMMENDED_METHODS_PER_SPECIALISM on an explicit promotion path to REQUIRED_METHODS_PER_SPECIALISM at v6.0 rc.1 GA. A minimal example that trips the validator teaches the wrong pattern; the right fix is to show the full required shape from the start, with stubs clearly marked for production wiring.

Drafting PR: expand hello_seller.py to all 9 methods, update docstrings to correctly distinguish hard/soft required, add dispatch-path smoke tests. Raised as PR #531.

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Triaged by Claude Code. Session: https://claude.ai/code/session_01SQEG3PCARK4eKHBbqu4fTS

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