fix(browser): preserve list paging and provider error contracts

[rudycelekli]

The Kernel browser list tool truncated matching sessions with limit/offset but always reported no next page. It also swallowed provider failures and cancellation, returning a successful empty or partial list. Report the remaining-page metadata and propagate retrieval errors; retain stale-record cleanup for confirmed HTTP 404 responses.

Eight regression/control cases exercise the public tool with committed migrations, real Drizzle ownership queries and the actual Kernel SDK against a local HTTP fixture. Four fail on the baseline and all eight pass after the fix. Controls cover final, exact-limit and empty pages, status filtering, default listing, workspace isolation and native 404 cleanup. HTTP 401, HTTP 503 and SDK cancellation now surface without removing the affected owned session. No live provider was accessed.

Exact final pnpm check passes all six tasks (96 files, 884 tests). The unchanged author-fork Checks workflow passed frozen install, all check tasks and complete runtime evaluations/gates including cleanup. Its actual merge checkout has the same tree as this signed source.

A supplementary author-fork production build checked out this exact signed head and passed frozen install and the unchanged pnpm build command, with a cache miss, TypeScript and all 14 generated static pages. It used public synthetic build fixtures; no live provider/deployment. A nonfatal parallel cache reservation warning is retained in the logs. Local build output is blocked by disk exhaustion; local Docker cleanup is unreliable. Upstream workflow authorization is separate and is not claimed green.

Pending #141 changes this file for Notte support; it retains the existing Kernel list behavior. This patch corrects the independent Kernel response contract.

AI assistance was used for investigation, implementation, tests and review under the submitting account. Signed DCO commits included.