Add recent run list trigger and PR filters

[121watts]

Summary

depot ci run list gets the same recent-run filters the API just learned.

What was happening

The run list command could show recent runs and narrow by status, repo, and SHA, but users still had to visually scan when they wanted a specific trigger type or a pull request. A bare PR number is not enough context because PR numbers are repository-scoped.

What happens now

depot ci run list supports --trigger and --pr. The PR flag requires --repo, passes through to the CI API, and the help/examples show the intended recent-discovery usage.

Anything else?

Pairs with the API change in https://github.com/depot/api/pull/3601. Branch/ref filtering stays out of this slice until we decide whether the user-facing contract should mean push branch, raw git ref, or PR head/base branch.

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Note

Medium Risk
Changes the public protobuf contract for ListRuns and updates CLI flag behavior, so mismatched server/client versions or incorrect filter semantics could alter what runs are returned.

Overview
Adds recent run discovery filtering for CI run listings by introducing trigger and pr fields on ListRunsRequest (and updating service docs to clarify it’s newest-first discovery, not historical search).

Plumbs these new filters through the Go API wrapper (CIListRunsOptions -> ListRunsRequest) and exposes them in depot ci run list via --trigger and --pr, including validation that --repo is required when --pr is provided; tests are updated/added to assert the new flags and request fields are passed across pagination.

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[linear-code]

DEP-4345 M3: Add recent ListRuns filters