ujx1Bf conversation payload

# `ujx1Bf` conversation payload

After `json.loads(arr[0][2])` the tree is:

```
data[0]                    conversation envelope
  [1]                      turns[]  (oldest first)
  [2][1]                   title (string)
  [2][7]                   [?, modelFingerprint, modelLabel]  e.g. [2, "e6fa…", "Pro"]
  [3]                      shareId  e.g. "eba53f5c0e60"
  [4]                      [publishedUnixSeconds, nanoRemainder]
  [6]                      share thumbnail URL (optional)
data[1]                    unused
data[2]                    unused
```

Each `turn`:

```
turn[0]                    [conversationId, requestId]
turn[1]                    parent pointer [conversationId, prevRequestId, prevResponseId] or null
turn[2][0][0]              user message (full string)
turn[2][0][4]              attachments
                           video example:
                           [[null, null, null, [[null, 2, "file.mp4", null,
                             [3, "generic", "Invalid file ID"], null, null, null, 1,
                             [uploadUnix, nano], null, "video/mp4"]]]]
turn[3]                    model response
  [0][0][1][0]             Gemini reply as Markdown (canonical body — use this)
  [1]                      Google Search queries, e.g. [["Harvey AI valuation 2025 2026", 1], …]
                           or null
  [3]                      responseId  e.g. "rc_59809d1bbf8c0840"
  [4], [5]                 tool-use chrome (Google Search labels) or null
  [14] / [17]              model fingerprint (repeat of envelope)
turn[4]                    [messageUnixSeconds, nanoRemainder]
```

IDs to archive: conversation `c_…`, request `r_…`, response `rc_…`, share id,
model fingerprint, `skid` query param(s).

Unix seconds → UTC with `datetime.utcfromtimestamp(seconds)`. Remainder is
nanoseconds; keep it in the identifiers table, not in the displayed clock.