fix(fs): address review — rename to dsh-fs-policy, fs/*-intent events, RFC currency, ENOTDIR

Rename per review naming decisions:
- package dsh-file-context → dsh-fs-policy (dir, package name, plugin name,
  tsconfig refs, importers, type-equiv manifest, generated catalog + module-graph)
- events fs/write-expectation → fs/write-intent, fs/edit-expectation → fs/edit-intent
  (fs/observed unchanged); type FsWriteExpectation → FsWriteIntent, "expectation"
  wording → "intent" throughout
- exported FileContextExec → FsPolicyExec

Make the implemented RFCs describe what shipped, not the superseded designs:
the 2026-06-17 capability-seam + tool-schemas RFCs no longer place policy on
ctx.fs or use full/partial-view authorization, and the fsspec RFC's ctx.fileContext
service prose is rewritten to the fs/* event-gate reality (freshness-based auth).
Sharpen docs/rfc/implemented/AGENTS.md: a rename is a fact to fix IN PLACE — the
"new RFC" escape hatch is for macro decision reversals only, not renames.

Code fixes from review:
- fsio.ts resolveLocalTarget/probe translate ENOTDIR (a parent path segment is a
  file) into the structured FsError taxonomy instead of leaking a raw Node error;
  resolve reports FS_NOT_FOUND, probe reports absent. Regression tests proven to
  fail on the unfixed code.
- tool-fs HMR test now asserts prompt sections (not just tool schemas) are
  withdrawn on disposal.
- fs/observed is a plain (unguarded) ctx.emit: correct the fs-policy comment,
  filesystem.md, and tool-fs module doc that wrongly claimed the tool "contains"
  a throwing listener; a throw surfaces as the tool's isError result.
- drop the false "loaded by the default product config" claim (no config wires
  the fs tools yet), the duplicate ctx.bash service-map row, the stale
  FileReadRequest catalog link-map entry, and the fs/fs README EOF blank line;
  correct the dsh-fs package.json description.

docs/module-graph.md

@@ -22,8 +22,8 @@ graph TD
   agent --> session
   compact --> llm
   compact --> session
-  file-context --> fs
   fs-local --> fs
+  fs-policy --> fs
   llm-replay --> llm
   llm-replay --> session
   session-persistence --> session
@@ -120,8 +120,8 @@ graph TD
 | `system-prompt` | `llm` |
 | `agent` | `brand`, `llm`, `session` |
 | `compact` | `llm`, `session` |
-| `file-context` | `fs` |
 | `fs-local` | `fs` |
+| `fs-policy` | `fs` |
 | `llm-replay` | `llm`, `session` |
 | `session-persistence` | `session` |
 | `compact-basic` | `agent`, `compact`, `llm`, `session` |