Add job-to-Linear issue table to nemo-ci failure reports

Requests:

• Add a job-to-Linear issue correspondence table to the nemo-ci failure follow-up output.
• When nemo-ci runs a pipeline, reports failed jobs, and opens/updates Linear tickets, emit a searchable table that maps each failed job to the Linear issue tracking it.
• The table should include at least: pipeline, failed job name, job URL, action (open, update, close when relevant), Linear issue identifier, Linear issue URL, title/root-cause bucket, and assignee when known.
• Make this available in the Slack follow-up and/or generated artifacts so users can quickly search for “which ticket owns this failed job?”.

Implementation notes:

• Current flow appears to bucket failures into failure_buckets.json, reconcile them in scripts/agent/linear_reconcile.py, write/open tickets through scripts/linear/linear_write.py, and render Linear follow-up messages through scripts/slack_notification/follow_up_reconcile.py.
• linear_action_plan.json already carries per-test {name, job_url} on open/update actions, and linear_write.py stamps linear_identifier/url back onto opened actions after issue creation.
• A durable implementation should preserve that per-test mapping after writes, then render/export rows like job -> Linear issue rather than only grouping by assignee or root-cause bucket.

Related context:

• AM-516
• AM-517

Trace the flow from failure_buckets.json through scripts/agent/linear_reconcile.py and scripts/linear/linear_write.py into scripts/slack_notification/follow_up_reconcile.py. Start by checking how per-test name and job_url data is preserved and how linear_identifier and url are stamped onto actions. Done means the Slack follow-up or generated artifact contains searchable rows mapping each failed job to its Linear issue, including the requested fields.