Triage CLI: progress indicator showing where we are in the pipeline

[potiuk]

The terminal output during a triage session does not make it obvious where we are in the pipeline (fetching, classifying, awaiting decision, applying). Add a clear indicator/explanation per PR and per batch.

Suggested format (open to alternatives)

• Batch-level: Triaging 5/27 PRs · fetched 120 reviews so far (replaces the current "next page" line, including the running total of items fetched).
• PR-level: [3/27] #66444 — step: classify → propose comment.

Why: in long sessions it is easy to lose track of which PR is current and how much remains; also helps when interrupted/resumed.

Related: clickable PR links (separate issue) for the same lines.

[potiuk]

Status check against main — the batch-level half is done; the per-PR counter is not.

Done — batch level. interaction-loop.md:118 renders a group header carrying position and size:

Group 3 of 8  —  deterministic_flag → draft  —  27 PRs

Also done — the running total. fetch-and-batch.md:213 emits one line per page: page N: fetched M PRs (total: K). That covers the "including the running total of items fetched" part of the request — counting PRs rather than reviews, which is the more useful number.

Not done — PR level. The drill-in header (:199) is:

PR #65471   "Add support for new db dialect"

No [3/27] position, and no "step: classify → propose comment" stage marker.

This is the half the rationale actually asks for — "in long sessions it is easy to lose track of which PR is current and how much remains" describes walking a group with [E]ach, which is exactly where there is still no counter. The group header tells you where you are between groups, not within one.

Remaining work, narrowed: add a position indicator to the individual drill-in header when it is reached via [E]ach or [P]NN — the index within the current group and the group size.

The related clickable-PR-links issue is done (#1049).

[CAOShurong]

I'd like to take the remaining per-PR slice. I'll update the [E]ach / [P]NN drill-in contract and add eval fixtures covering first, middle, last, and original-group positions. If that matches the narrowed scope above, please assign this to me.