harness(phase-0): sudo-free Host-header path + chat_history + envelope replays

[HongmingWang-Rabbit]

Summary

Phase 0 of the long-term harness roadmap — three changes that bring the local harness from "covers what staging covers minus the SaaS topology" to "exercises every surface we shipped this session against the prod-shape `Dockerfile.tenant` image."

1. Drop the `/etc/hosts` requirement

Replays previously needed `127.0.0.1 harness-tenant.localhost` in `/etc/hosts` to resolve the cf-proxy. That gated the harness behind a sudo step on every fresh dev box and CI runner. cf-proxy nginx already routes by Host header (matches production CF tunnel), so the no-sudo path is to target loopback `:8080` with `Host: harness-tenant.localhost` set as a header.

New `tests/harness/_curl.sh` centralises this — `curl_anon`, `curl_admin`, `curl_workspace`, and `psql_exec` wrappers all set the right Host + auth headers automatically. `seed.sh`, `peer-discovery-404.sh`, `buildinfo-stale-image.sh` updated to source it. Legacy `/etc/hosts` users still work via env-var override.

2. Fix the `seed.sh` FK regression that blocked DB-side replays

`POST /workspaces` ignores any `id` in the request body and generates one server-side. `seed.sh` was minting client-side UUIDs that never reached the workspaces table, so any replay that INSERTed into `activity_logs` (FK-constrained on `workspace_id`) failed with `workspace not found`. Capture the returned id from the response instead.

3. Two new replays cover the surfaces shipped this session

`replays/chat-history.sh` — exercises the full SaaS-shape wire that PR #2472 (peer_id filter), #2474 (chat_history client tool), and #2476 (before_ts paging) ride on. 8 phases / 16 assertions:

• Basic peer_id filter (DESC ordering, oldest/newest)
• Limit clamp
• before_ts paging (strict less-than, cursor walk-back)
• OR clause covering both source_id and target_id
• Malformed peer_id → 400
• Malformed before_ts → 400 + RFC3339 example
• URL-encoded SQLi-shape peer_id → 400 (UUID validation rejects pre-SQL)

`replays/channel-envelope-trust-boundary.sh` — exercises PR #2471 + #2481 by importing from `molecule_runtime.*` (the wheel-rewritten path) so it catches "wheel build dropped a fix that unit tests still pass." 5 phases / 11 assertions:

• Malicious peer_id scrubbed from envelope
• `agent_card_url` omitted on validation failure
• XML-injection bytes scrubbed
• Valid UUID preserved + URL builds canonically
• `_agent_card_url_for` direct gate

`run-all-replays.sh` auto-discovers `replays/*.sh` — no registration needed.

Verification

```
$ ./run-all-replays.sh
[run-all] booting harness...
[run-all] seeding workspaces...
[run-all] ━━━ buildinfo-stale-image ━━━ PASS
[run-all] ━━━ channel-envelope-trust-boundary ━━━ PASS (11/11 against wheel 0.1.79)
[run-all] ━━━ chat-history ━━━ PASS (16/16)
[run-all] ━━━ peer-discovery-404 ━━━ PASS
[run-all] Replay summary: 4 passed, 0 failed (of 4 total)
```

Test plan

• `./up.sh` works without /etc/hosts edit
• `./seed.sh` writes UUIDs that match the workspaces table
• `./run-all-replays.sh` 4/4 PASS end-to-end
• Legacy /etc/hosts users still work via env-var override
• CI on this branch
• Roadmap follow-ups: Phase 2 (multi-tenant + CI gate), Phase 3 (real CP), Phase 4 (Miniflare + LocalStack)

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