Discovery + search verbs: integrations, github/slack/linear/sentry, session search/steps, config create

[hbrooks]

Adds the discovery + search verbs over the /v1 surface that merged in ellipsis-dev/ellipsis#5623.

New commands

• agent integrations (GET /v1/integrations): INTEGRATION / STATUS / DETAILS table across github, slack, linear, jira, sentry.
• agent github repos / agent github members (GET /v1/github/repos, /v1/github/members): members shows the linked Slack user id when a link row exists.
• agent slack channels / agent slack members (GET /v1/slack/channels, /v1/slack/members): a 404 maps to a friendly "Slack is not connected" error; members shows the linked GitHub login.
• agent linear teams (GET /v1/linear/teams, same 404 mapping) and agent sentry orgs (GET /v1/sentry/organizations; empty list, never 404).
• agent session search <query> (GET /v1/sessions/search): four-arm search (steps / recap / pr / similar), one block per result session with author, age, matched arms, and the best snippet. Flags: --author (login resolved via /v1/github/members; unknown logins error with the known roster), --agent, --source, --repo, --status, --scope, --session, --since/--until (ISO or "today" / "yesterday" / "N days ago"), --limit. PR-shaped queries are documented in --help.
• agent session steps <sessionId> (GET /v1/sessions/{id}/steps): chronological one-line-per-step transcript; --json for full payloads.
• agent session list --author <login>: same resolver, passes author_id.
• agent config create --repo <name> (--file <path> | --template <slug>) [--path ...] (POST /v1/configs): prints the created PR URL.

Notes

• Types mirror the merged backend models (integrations_service.py, sessions_search_service.py) exactly; still hand-rolled pending @ellipsis/sdk.
• Repeatable facet flags (source/status/scope) validate client-side so typos fail with the full value list instead of a 422.
• All new verbs support --json; no em/en dashes in new user-facing strings.
• Docs: landing reference/cli page updated in ellipsis-dev/ellipsis#5624.

Testing

• vitest: 145 passing (~35 new: arg coercions, natural dates, relative age, integration rows, author resolution, search/steps URL building, result + step formatting), tsc --noEmit and tsup build clean.
• Exercised live against production: every discovery verb, search (steps arm + facets), steps rendering on a real transcript, --author resolution and its unknown-login error.