Release reader ergonomics improved; README trimmed

Minor Changes

• ca636fa: Improve the release-reader ergonomics for get, latest/tail, and list (#303, #304):
  • get <id> --json now surfaces media[] (with the R2-mirrored r2Url) when a release has media, plus a contentTruncated: true hint so callers know the body was projected to an excerpt and --full exists. Previously the slim shape dropped media entirely with no signal it existed, forcing a round-trip to --full or the raw API to verify media presence. --full is unchanged.
  • latest/tail gain --limit (an alias for the existing --count) so the absence of --limit — which works on other commands — no longer errors with "unknown option". Both clamp to the server's [1, 100] window, and a one-shot listing that fills the requested window now prints a truncation hint to stderr (raise --limit, narrow with --since/--until/--source/--org, or for --product feeds, page with the surfaced --cursor).
  • latest --product is cursor-paginated; a new --cursor flag pages through it deterministically (the global latest feed has no cursor — it is count-capped — so --cursor errors there).
  • releases list now shows a Releases per-source count column in the text table, so "how many releases does this source have?" is answerable without dropping to --json (which already carried releaseCount) or the raw API.

Patch Changes

• e045fe0: Trim the README to a leaner npm landing page (291 → ~130 lines): merge the install paths, condense the shell-completion and output-format prose into pointers to --help, drop the closed-beta admin-triage detail, and consolidate the auth sections. Reframe sign-in messaging around its present-day value — following orgs/products and a personalized feed — with read-only keys explicitly non-write/non-admin (and a path to higher rate limits), rather than leading with the closed-beta write/admin caveat.