docs: add evaluation-readiness index page

[bonaventure001]

Summary

Closes #433

Adds docs/evaluation-readiness.md — a single index page linking the payment expectation
guide, testing standard, CI guidance, acceptance criteria audit template, self-assessment
form, and reviewer checklist, which were previously scattered across README, the PR template,
and separate docs. README's docs index links the new page.

Issue scope

Acceptance Criterion	Status	Implementation Evidence	Tests	Notes
Evaluation-readiness index page is added.	✅ Done	docs/evaluation-readiness.md	N/A	Docs-only change
Payment expectation guide is linked.	✅ Done	docs/evaluation-readiness.md § "1. Payment expectations" → docs/meaningful-change-review.md	N/A
Testing standard is linked.	✅ Done	§ "2. Testing standard" → testing.md, module-test-matrix.md, coverage-baseline.md	N/A
CI guidance is linked.	✅ Done	§ "3. CI guidance" → pre-pr-verification.md, pre-submission-verification.md, local-verification.md	N/A
Acceptance criteria audit is linked.	✅ Done	§ "4. Acceptance criteria audit" → .github/checklists/acceptance-criteria.template.md	N/A
Self-assessment and reviewer checklist are linked.	✅ Done	§ "5. Self-assessment" → contributor-self-review.template.md; § "6. Reviewer checklist" → contribution-quality-gate.md (doc + checklist)	N/A

Affected packages / apps

• docs/
• apps/web
• Other (list):

Testing performed

Docs-only change — no build/test surface affected. Verified by inspection: every doc and
checklist file linked from the new index page was confirmed to actually exist in this repo
(docs/ or .github/checklists/) before linking, with one exception noted below.

Security impact

• This PR touches secret handling, callback URLs, network selection, or contract
  admin/authorization logic.
• No security-relevant surface touched.

Documentation impact

• Docs under /docs updated for this change.
• README updated (new package, script, or workflow).
• No user-facing behaviour changed — no docs update needed.

Risk / follow-ups

The issue also asks for a "communication policy" to be linked. This repo doesn't have one —
docs/meaningful-change-review.md already references a "Payment-Period Conduct Note" that
lives in the pocketpay-contracts repo instead, since it's shared across the whole PocketPay
GrantFox campaign rather than duplicated per-repo. I confirmed that doc exists there
(pocketpay-contracts/docs/payment-period-conduct.md) and linked to it directly rather than
inventing a duplicate copy in this repo. Flagging in case a maintainer would prefer a local
copy instead of a cross-repo link.