docs: add payment-period conduct guidance

[jd5073356-max]

Pull Request

Issue Reference

Closes #532

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Summary

Adds docs/payment-period-conduct.md: guidance for how contributors should raise payment-status questions, what self-review to do first, and how this repo's review relates to GrantFox's own evaluation/payment process. Linked from README.md and CONTRIBUTING.md.

Contract Functions Changed

none — documentation-only PR.

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Tests Added or Updated

• N/A — documentation-only change, no contract logic touched.
• N/A — docs/test-coverage.md not affected (no test changes).

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Security Considerations

No security impact — this PR only adds/edits Markdown documentation (docs/payment-period-conduct.md, README.md, CONTRIBUTING.md). No contract, script, or CI file is touched.

Security checklist (contract changes only)

N/A — no contract changes in this PR.

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Commands Run

cargo fmt --check

• make verify — not applicable (docs-only; no Rust files changed)
• cargo fmt --check — passed (confirms no accidental non-doc changes)
• cargo clippy --tests -- -D warnings — not applicable (no Rust files changed)
• cargo test --workspace — not applicable (no Rust files changed)

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CI Status

• No CI-relevant files changed (Markdown only); repository's only workflow is an auto-merge trigger, not a build/test gate.

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Traceability Table

Criterion ID	Criterion Text	Changed Function(s)	Test(s)	Edge Cases Covered	Status
AC-1	Payment-period conduct guidance is added	N/A (docs)	N/A	New file docs/payment-period-conduct.md	✅ Met
AC-2	Repeated spam or complaints are discouraged	N/A (docs)	N/A	"What to avoid" section explicitly calls out repeating the same question across threads/channels and public escalation before self-review	✅ Met
AC-3	Contributors are asked to self-review first	N/A (docs)	N/A	"Before asking about payment status" section requires checking acceptance criteria, the Contribution Quality Gate, PR template completeness, and CI status first	✅ Met
AC-4	GrantFox evaluation process is referenced	N/A (docs)	N/A	"How GrantFox evaluation works, from this repo's side" section distinguishes this repo's code review from GrantFox's own evaluation, scoring, and payment process	✅ Met
AC-5	Tone is professional and firm	N/A (docs)	N/A	Doc avoids hedging language; "Tone" section states the expectation directly	✅ Met
AC-6	README links to the guidance	N/A (docs)	N/A	README.md Documentation list + Contributing section both link to docs/payment-period-conduct.md	✅ Met