fix(web): resolve optimistic edit refresh race

[szzhoujiarui]

Description

Fix the first edit attempt for a recently persisted non-initial user message. loadSession() now returns its hydrated message snapshot, and the edit flow resolves an optimistic negative ID from that snapshot directly instead of immediately reading a stale React state ref.

A focused regression test covers the race where the local state still contains the optimistic ID after the refresh has returned the persisted message.

Related Issues

• Closes [Bug]:非首条请求在首次编辑改动时无法保存 #739

Module(s) Affected

• agents
• api
• config
• core
• knowledge
• logging
• services
• tools
• utils
• web (Frontend)
• docs (Documentation)
• scripts
• tests
• Other: ...

Checklist

• I have read and followed the contribution guidelines.
• My code follows the project's coding standards.
• I have run pre-commit run --all-files and fixed any issues.
• I have added relevant tests for my changes.
• I have updated the documentation (if necessary).
• My changes do not introduce any new security vulnerabilities.

Additional Notes

Validation completed:

• npm run test:node: 367 tests passed
• node ./node_modules/typescript/bin/tsc --noEmit: passed
• ESLint on the three changed files: passed
• git diff --check: passed

The repository-wide ESLint run currently reports existing errors in unrelated modules; this change adds no lint findings in the files it modifies.