docs: anchor each subsystem page to its package group; make group READMEs thin tables

core.md read as a type grab-bag: LLM wire vocabulary up front, the agent/loop story buried, and no correspondence to packages/core. It now opens on the packages/core control spine — the package-by-package loop map with a Page column into session/system-prompt/tools/scope — and keeps only what the spine group declares plus the repo-wide patterns: the Agent handle with its delivery/cancellation/interception contracts, the SessionEvent envelope, branded ids, the …Map pattern. The conversation vocabulary (Message/ContentBlock, the model request, adapters — 17 type-equiv blocks) moves to llm-streaming.md, which now declares packages/llm end-to-end; the duplicate ContentBlockMap paste near its seam section folds into the moved section, and the manifest, LINK_MAP, README table rows, website label (Core data structures → Core), and inbound anchors follow.

Every packages/<group>/README pair is now a thin front door in one shape: a why-first intro (bash's seam-pattern-first paragraph rewritten as 'shell execution for the agent'), the package table, and a closing pointer to the owning docs/subsystems page — the bash-style table stays the load-bearing middle. Load-bearing trailing paragraphs relocate rather than vanish: the fs no-timeout rationale becomes a filesystem.md section (both languages), session's four sectioned tables merge into one 12-row table, examples' legacy-bin H2 collapses to a pointer at jsonrpc-demo's README, and design rationale that already lives in an Agent Note or subsystem page is now linked instead of restated. All 40 pair records re-recorded.

docs/subsystems/filesystem.md

@@ -256,6 +256,10 @@ type FsErrorCode =
 
 `FS_NOT_DIRECTORY`, `FS_PERMISSION_DENIED`, and `FS_IO_ERROR` are used by directory listing to distinguish an existing non-directory target, a denied listing, and an unexpected backend I/O failure. `FS_SANDBOX_DENIED` is a POLICY refusal from a sandbox-enforcing backend (`dsh-fs-sandbox`) — the mode fence denied a write/edit — distinct from `FS_PERMISSION_DENIED` (the host kernel refusing). `FS_NOT_OBSERVED` means the policy plugin has no prior-observation record for this owner (or a `createIfAbsent` hit an existing file). `FS_STALE_VERSION` means the backend version no longer matches the observed one (or an edit hit a missing target). Freshness authorization has no partial/full distinction, so there is no `FS_PARTIAL_OBSERVATION`.
 
+## No timeouts on file IO
+
+`read`/`write`/`edit` take **no** `timeoutMs`, and the provider seam arms no deadline — unlike bash and web (which consume [`@deepseek-ai/dsh-timeout`](../../packages/util/timeout/README.md)) and the bash-backed `glob`/`grep` (whose declared `timeoutMs` is enforced by `@deepseek-ai/dsh-timeout-policy`): those are process-backed, where a deadline can really kill the work. A local syscall is best-effort-abortable at most — a timeout could not force an in-progress `fsync`/`rename` to stop, so a deadline here would be a knob that cannot deliver on its promise, and an implicit default in the exact place explicit-over-implicit forbids. Both reference agents (Claude Code, Codex) leave file IO untimed for the same reason; cancellation still propagates through the tool-execution signal for best-effort abort at syscall boundaries.
+
 ## The service and the plugin
 
 `FileSystem` (`ctx.fs`, abstract) owns the provider primitives: `resolve`, `processPath`, `fileUrl`, `contains`, `stat`, `lstat`, `readText`, `streamText`, `listDir`, `writeText`, and `editText`. `dsh-fs-policy` registers **no service** — it is a plugin that adds policy through the `fs/*` event gate: it decides the write/edit intent waterfalls (supplying `createIfAbsent`/`replaceIfVersion`/`{ version }` or throwing `FS_NOT_OBSERVED`) and records on `fs/observed`. The executor is `dsh-tool-fs`: it reads/writes/edits through `ctx.fs`, dispatches the waterfalls, and emits the recording event. The generated [`ctx.fs` section](#ctxfs--filesystem-abstract-seam) below shows the exact signatures.