fix(wavey-gist): use new files-snapshot payload for create endpoint

[spalen0]

Summary

utils/wavey_gist.upload_to_gist was posting the legacy payload shape ({title, markdown}) to Wavey Gist. The API now rejects unknown fields with HTTP 400:

Legacy gist fields are no longer supported. Send a files snapshot and include expected_snapshot_sha256 for updates.

raise_for_status() turned the 400 into requests.HTTPError, which the existing try/except (requests.RequestException, ValueError) swallowed. The caller (format_explanation_line in utils/llm/ai_explainer.py) then fell through to ⚠️ Couldn't post full report in the Telegram message. The Telegram summary still shipped — only the linked detail was lost.

This is the same payload that powers every AI report link in production (e.g. timelock alerts, governance-proposal walkthroughs). Whenever an explanation had a detail long enough to be sent to gist, the team got the warning instead of a working link.

Reproduction (against the prod WAVEY_GIST_API_KEY)

POST https://api.wavey.info/api/v1/gists
{ "title": "test", "markdown": "# test\n\n..." }
→ 400 {"error":{"code":"invalid_request",
      "message":"Legacy gist fields are no longer supported. ..."}}

Fix

Switch the create payload to the documented files-snapshot shape and put the report under README.md (the API's preferred primary filename, so the rendered page opens with the content):

{
  "title": "AI Transaction Analysis",
  "files": { "README.md": { "content": "# AI Transaction Analysis\n\n..." } }
}

Response shape ({url, id, primary_file, files, snapshot_sha256, ...}) is otherwise compatible — only the request body needed to change.

Live-validated with the production key after the patch: Status 201, gist renders with the correct title and README.md as the primary file.

Tests

• test_successful_upload: assert the legacy markdown field is gone and the content lives at files[README.md].content.
• test_no_title_sends_raw_content: reworked to match the new shape.
• test_http_error_returns_empty (new): covers the exact failure mode that triggered this incident — the function must keep alerting and return "" so the in-Telegram summary still ships even when gist is down or its schema changes again.

All 7 test_wavey_gist.py cases pass; ruff format and ruff check clean.

Backfill

Pushed a follow-up gist for the InfiniFi LongTimelock call (tx 0xf61f9e5af62d4ec67b8b6ef71524226236e5d30acb1945531181b4e497c765f3) that surfaced this — see the [Full details] link posted in the original thread.