[31b4]

Closes #175

Summary

Prepare the requested major release v4.0 for the rebuilt Investments experience, cash-linked trades, performance/history, unified transaction composer and MCP split review drafts. The release notes also cover the Dashboard refresh, decimal balance correctness, currency labels, pointer cursors and migration-runner fix since v3.3.

Changes

• Set the root application version and both root lockfile version fields to 4.0; dependencies and independent MCP versions are unchanged.
• Replace Unreleased with a grouped v4.0 recap and four highlights, retaining an empty Unreleased section and all published release history.
• Document each of the six added SQL migrations, preserve both original 017 names, and describe backup/rehearsal, the write-free window, coordinated API → MCP → client rollout and legacy-data boundaries.
• Update README release/changelog links for planned UTC publication on 2026-10-20. The draft GitHub release notes are extracted verbatim from this changelog section.

Verification

• Pinned Node 22.23.2: full npm test passed: 538 client, 225 API, 51 MCP, 29 deployment and 322 compiled Worker/D1 integration tests. The two existing opt-in history benchmarks remain skipped.
• npm run typecheck passed for all workspaces and integration tests.
• VITE_API_AUTH_MODE=public VITE_API_DOMAIN=localhost:8787 npm run build passed, including PWA generation; Vite retains its existing bundle-size advisory.
• npm run lint -w client -- --max-warnings=0 passed.
• Node 26.5.0: all 538 client tests passed.
• Audited all 27 merged PRs (seven main PRs and 20 investment child PRs) and all 84 non-merge commits in v3.3..origin/main. Every PR has a link in the new section; all commits belong to those merged changes, with no direct main commits. All six new SQL migration filenames have individual upgrade notes.
• Parsed package files to confirm all three root versions agree on 4.0 and the lockfile changes only those two version fields. Published changelog history remains identical; README anchor/date and extracted release notes agree.
• git diff --check passed; reviewed the four-file release diff.

Merge and publication require explicit user approval. Before publication, retarget the draft to the reviewed merge commit and verify the UTC publication date against the changelog. Deployment remains separate.