[Improve] Attribute tasks to users or named automations

[roomote-roomote-v1]

Opened on behalf of Matt Rubens. Follow up by mentioning @openmote, in the web UI, or in Slack.

What changed

Tasks (and Roomote-linked analytics/PR attribution that reuses the same helpers) are associated with either a matched product user or the name of the automation that started them.

• Matched humans keep their own user identity.
• Product-owned automation launches stamp a specific name when known (PR Reviewer, Resolve PR Conflicts, Suggest Ideas, Triage Dependabot Alerts, etc.).
• Analytics Tasks By User and task attribution display surface those names as their own series instead of only free Automations/Roomote.
• Unnamed automatic work falls back to Automations. Residual unlinked external identities keep their own label.

Why this change was made

The Tasks By User chart mixed people with generic automation/bot labels, which hid which automation started the work. Direction is user or automation name.

Impact

• New automation-started tasks show named automation when type or suggestion source is known.
• PR review / conflict-resolution background tasks attribute to PR Reviewer / Resolve PR Conflicts rather than the bot login.
• Historical rows without a stamped display name still land in Automations until re-run or backfill.
• Task-list creator filter still has a single automatic bucket; chart/detail naming is the primary surface here.

Screenshots

[roomote-roomote-v1]

No new code issues found. See task

[roomote-roomote-v1]

Superseded by #14, which absorbs this PR's automation-name resolver and analytics dimension changes and additionally consolidates the creator filter, PR attribution line, and task-list surfaces onto the same initiator model while removing the fallback user ids stamped on automation tasks. Closing in favor of that PR.