Add a gated Known Limitations and Deferred Work section to every package README

Every packages/*/* README now carries a canonical '## Known Limitations and
Deferred Work' section: condensed, evidence-backed bullets for consumer-visible
gaps (unimplemented features, platform caveats, MVP cuts) and consciously
postponed work (TODO/FIXME/XXX markers, RFC deferrals still open). The ten
pre-existing ad-hoc variants ('What is NOT here (TODO)', 'Deferred',
'Limitations (MVP)', 'Known limitations (tracked TODOs)', ...) are normalized
into the canonical heading.

A new doc-sync gate, scripts/verify-readme-limitations.ts, enforces the shape:
exactly one limitations-like heading per package README, byte-equal to the
canonical h2, with at least one bullet; near-miss headings fail so variants
cannot creep back. Packages with genuinely nothing to declare (dsh-brand,
dsh-timeout, dsh-subagent-mock, dsh-app-boot) are whitelisted in the script and
must NOT carry the section; whitelist entries are validated against the scanned
package set so a rename fails loud.

Wired into the doc-sync chain (package.json) and the run-gates doc-sync leaf
set; the standing rule lands in packages/AGENTS.md and the adding-a-package
cookbook; decision record in
docs/rfc/implemented/process/2026-07-10-readme-known-limitations-gate.md
(RFC index regenerated).

Also fixes two stale '(deferred)' markers claiming dsh-compact-basic is
unimplemented (the dsh-compact seam README's package table and the seam's
module doc comment).

packages/web/tool-web/README.md

@@ -33,3 +33,9 @@ Each tool is registered independently; a product that wants only one disables th
 Tool registration follows product **enablement**, not backend availability. A tool stays visible even when its selected provider is missing, misconfigured, ambiguous, or temporarily unavailable; the seam resolves the provider at execution time and execution fails with a structured `WebError` (e.g. `WEB_PROVIDER_UNAVAILABLE`, `WEB_PROVIDER_AMBIGUOUS`), which `ToolRegistry.execute()` turns into an error tool result the model can read and hooks/UI can route on. This keeps the model schema stable without making plugin load order, credential state, or HMR timing part of the model-facing contract. To remove a web tool entirely, disable it here in config.
 
 The tool never calls a provider's `status()` and never enumerates providers — its only execution path is `ctx.web.search()` / `ctx.web.fetch()`, and provider unavailability reaches it as the structured `WebError` codes selection throws at execution time. Provider selection stays entirely inside the seam, with one owner.
+
+## Known Limitations and Deferred Work
+
+- **`htmlToMarkdown` is a minimal regex converter, not an HTML parser** — it strips script/style/noscript, keeps headings/bullets/links, and decodes about a dozen named entities; tables, images, and nested formatting are lost.
+- **The model-facing surface is minimal by design, with promotions deferred** — `max_results` stays a config bound (not a model argument), and `web_fetch` takes only `url` (no `format`/`prompt`/LLM-summarization mode); both are named later steps in [the seam RFC](../../../docs/rfc/implemented/architecture/2026-06-24-web-capability-seam.md).
+- **No permission gating** — both tools execute without any permission prompt or policy; integration awaits the deferred permission system, with the owner (a `tools/execute` plugin, provider config, or both) undecided.