Add a general typed tool-progress contract so long-running non-exec tools can emit public channel progress without overloading model-facing tool content.
`web_fetch` now uses the generic delayed progress helper: it shows `Fetching page content...` only when the fetch is still pending after five seconds, clears the timer on completion/abort, passes the abort signal into guarded fetch, and avoids provider fallback or cached success after cancellation. The subscriber path accepts only explicit `visibility: "channel"` and `privacy: "public"` progress metadata, while untyped tool partials and exec output keep their existing behavior.
Docs now explain typed progress, delayed producer examples, and the `web_fetch` timing behavior.
Proof: `pnpm test src/agents/tools/web-tools.fetch.test.ts src/agents/embedded-agent-subscribe.handlers.tools.test.ts -- --run`; `pnpm docs:check-mdx`; changed-file `pnpm exec oxlint ...`; `git diff --check`; autoreview clean.
