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Make the implemented RFCs describe what shipped, not the superseded designs: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  withdrawn on disposal.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.

packages/README.md

@@ -38,7 +38,7 @@ dsh-bash-local    ← dsh-bash                       (BashExecutor impl)
 dsh-tool-bash     ← dsh-bash, dsh-tools            (bash tool schemas)
 dsh-fs            ← dsh-llm, dsh-brand              (filesystem provider seam + fs/* events)
 dsh-fs-local      ← dsh-fs                          (FileSystem impl)
-dsh-file-context  ← dsh-fs                          (observed-state + freshness policy gate, no service)
+dsh-fs-policy     ← dsh-fs                          (observed-state + freshness policy gate, no service)
 dsh-tool-fs       ← dsh-fs, dsh-tools               (file tools + executor)
 dsh-llm-deepseek  ← dsh-llm                        (DeepSeek adapter)
 dsh-llm-pi-ai     ← dsh-llm                        (pi-ai-backed adapter)
@@ -78,7 +78,7 @@ The rule: **extension** plugins depend on interfaces, never on the concrete loop
 | `tool-bash/` | `bash` | Model-facing `bash`/`bash_output`/`bash_kill` tool schemas | (registers on `ctx.tools`) |
 | `fs/` | `fs` | Filesystem provider seam: text IO + atomic mutation primitives (optional version guard); owns the `fs/*` events | `ctx.fs` |
 | `fs-local/` | `fs` | Local-filesystem `FileSystem` implementation | (registers `ctx.fs`) |
-| `file-context/` | `fs` | Policy gate plugin: observed-state + read-before-edit + version-guarded write/edit via the `fs/*` event gate | (no service — `fs/*` listeners) |
+| `fs-policy/` | `fs` | Policy gate plugin: observed-state + read-before-edit + version-guarded write/edit via the `fs/*` event gate | (no service — `fs/*` listeners) |
 | `tool-fs/` | `fs` | Model-facing `read`/`write`/`edit` tools + executor (reads via `ctx.fs`, owns read windowing, dispatches `fs/*`) | (registers on `ctx.tools`) |
 | `compact/` | `compact` | Abstract compaction seam + `compact/*` events + `CompactionResult` | `ctx.compact` |
 | `compact-basic/` | `compact` | A backend: char/4 estimation + token-budget retention + `llm.stream()` summarization | (registers `ctx.compact`) |