feat: Update docs for Credible v2 API (Reshiram)

[makemake-kbo]

Summary

• keep the updated Reshiram v2 snippets in a clearer Diataxis shape: assertion pages stay example/reference-style, credible-std stays reference, and install details stay in the install guide
• restore the Assertions Book catalog/nav entries that were dropped in the branch
• move Assertions Book source links and the snippet import workflow from deprecated assertion-examples to credible-std/examples/assertions-book
• fix the ERC4626 deposit/withdraw snippet so callStart/callEnd match the current PhEvm.TriggerContext type

Related PRs

• Depends on Add canonical Assertions Book examples credible-std#62 for the new canonical example directory
• Deprecates the old source repo in Deprecate assertion-examples in favor of credible-std assertion-examples#24

Verification

• pnpm validate
• pnpm broken-links
• canonical snippets match credible-std/examples/assertions-book/assertions/src using the import workflow format

[linear]

ENG-2888 feat(docs): update docs for V2