refactor(fs): prune write-only fields and the dead routing knob from the seam

The fs seam split left four pieces of pre-split surface populated on
every call and read by nobody:

- STREAM_MIN_SIZE + FsIoInternals.streamMinSize in dsh-fs-local: the
  backend has no read routing (readWholeText/streamWholeText are
  separate primitives the caller picks), and the real 10 MiB routing
  constant lives in dsh-tool-fs's read tool. Delete the dead mirror and
  the knob whose JSDoc claimed an override that did not exist; the
  remaining FsIoInternals knobs stay (the atomic-write tests use them).
- FsTarget.inputPath: a "diagnostics only" field every backend and test
  fake had to fabricate, with zero production readers (policy and error
  messages use targetKey/displayPath). listDir gave children the bare
  entry name, which was nobody's input.
- FsEditOutcome.replacements/.replaceAll: replacements had no reader
  (the single-match policy is enforced by the FS_AMBIGUOUS_EDIT /
  FS_EDIT_NOT_FOUND throws, whose message keeps the internal count);
  replaceAll only echoed the replace_all argument back to
  formatEditOutput, which now takes it from the parsed args. The
  outcome shrinks to { version, before, after }, parallel to
  FsWriteOutcome's backend-discovered fields. Emitted text is unchanged
  for both branches (no snapshot churn).
- FileReadOutcome.limit/.version: formatReadOutput renders
  offset/lines/totalLines/truncatedByBytes only, and the fs/observed
  emit uses info.version directly.

Backends shed four fabrication obligations and gain none. Doc pastes
(core-data-structures/filesystem.md), the dsh-fs README resolve row,
and the test fakes shrink with the types. RFC moved to
implemented/simplification and amended to the shipped shape
(FsEditSpec -> FsEditRequest name fix; manifest rows needed no change).

packages/fs/tool-fs/src/read-render.ts

@@ -17,7 +17,6 @@
  */
 
 import { FsError } from '@deepseek-ai/dsh-fs'
-import type { FsVersion } from '@deepseek-ai/dsh-fs'
 
 /** Maximum characters returned for a single line. */
 export const READ_MAX_LINE_LENGTH = 2000
@@ -58,16 +57,12 @@ export interface WindowResult {
 export interface FileReadOutcome {
   /** 1-based first line requested. */
   offset: number
-  /** Maximum number of lines requested. */
-  limit: number
   /** Returned lines, already numbered. */
   lines: FileTextLine[]
   /** Total line count in the file, unless `truncatedByBytes` stopped scanning early. */
   totalLines: number
   /** Whether selected output hit the byte cap before EOF or the requested limit. */
   truncatedByBytes?: true
-  /** Opaque version of the file at read time. */
-  version: FsVersion
 }
 
 interface WindowAccumulator {