bug(examples/flowise-governance): flowise-flow.json fails to import on Flowise 2.x and 3.x

## Summary

The `examples/flowise-governance/flowise-flow.json` shipped in #3105 fails to import on Flowise 2.x and 3.x. Reported by an external adopter (jinweida) via email after trying to import the file on both major versions.

## Root cause

The JSON was authored by hand against Flowise's documented chatflow schema rather than exported from a running Flowise instance:

- Contains a non-standard top-level `_comment` key (real Flowise exports never include this).
- Node `data` (inputParams / baseClasses / anchors) does not match Flowise's live node registry, and every node is `version: 1` regardless of the installed node versions.
- The `_comment` and README claim "Flowise 2.x / 3.x" but the file was never validated against a live import.
- For accuracy: it is a 5-node flow (chatInput, customFunction, httpRequest, customFunction, chatOutput), not the 9-node flow the merge note described.

## What works (no change needed)

- `flowise-agentmesh` package: `GovernanceNode`, `AuditNode`, `RateLimiterNode`, `TrustGateNode` all exist.
- `governance_server.py` FastAPI sidecar (`/health`, `/govern`), `policy.yaml`, `requirements.txt`, README prose.
- The governance value lives in the HTTP Request node calling `/govern`, which is sound.

## What we need

A valid Flowise chatflow export that imports cleanly on a real, named Flowise version, replacing the hand-authored JSON. We cannot produce a genuine export without a running Flowise instance.

## Plan

- Invite the reporter (who runs Flowise 2.x and 3.x) to build the 5-node flow in his instance and contribute a verified export via PR.
- Validate the import on a clean Flowise instance and confirm the `/govern` round-trip before merge.
- Merge only when it imports cleanly and runs end to end.

## Acceptance criteria

- [ ] `flowise-flow.json` imports without error on a stated Flowise version (record the exact version in the README).
- [ ] Imported flow runs end to end against the sidecar (`/govern` allow and block paths).
- [ ] README updated with the exact validated Flowise version and the 2.x/3.x ambiguity removed.