Expose audited hardcoded tunables as plugin config

The audit swept every packages/*/* plugin for the new AGENTS.md
convention (no hardcoded tunables in plugins) and exposes each finding
as a defaulted, validated Config field. Defaults are the previously
hardcoded values throughout, so no deployment or golden changes.

- tool-fs (had NO Config): readLimit, readMaxLineLength, readMaxBytes,
  readStreamMinSize. The caps thread through ReadToolCaps/ReadWindow —
  read-render already documented that the consumer applies the caps, so
  they become explicit per-request fields.
- tool-web: searchMaxResults (WEB_SEARCH_MAX_RESULTS stays as the
  schemastery default). Also fixes the stale GREP_LIMIT references in
  search.ts and the web-capability-seam RFC (no such constant exists).
- bash-local: graceMs (SIGTERM->SIGKILL escalation grace). The
  RunInternals.graceMs test seam is gone: graceMs is now a required
  SpawnSpec field filled from config, so tests exercise the real
  config path and the defaults live in exactly one place.
- subagent-acp: disposeEofGraceMs / disposeGraceMs. The AcpRunSpec
  fields become required for the same one-defaulting-layer reason.
- session-persistence-sqlite: journalMode ('wal' default; the
  rollback-journal modes serve filesystems where WAL's shared-memory
  files do not work, e.g. network mounts).
- hooks-claude + hooks-codex: stderrSummaryMaxChars for the persisted
  hook/result stderr summary. The duplicated summarize() helpers merge
  into hook-protocol's summarizeStderr(stderr, maxChars), beside the
  HookResultRecord field it feeds, with the bound parameterized the
  same way runHook's defaultTimeoutMs already is.
- compact-basic: charsPerToken for the token estimator (default 4, the
  English-text heuristic; CJK-heavy deployments need ~1-2 or compaction
  fires far too late). Also corrects the BasicCompactService class doc,
  which claimed defaults the required-field config never had.
- fs-local: deletes the dead STREAM_MIN_SIZE constant and the dead
  FsIoInternals.streamMinSize seam — the read-routing bound lives in
  the consumer (tool-fs), where it is now config. This is item 1 of
  the proposed prune-write-only-fs-surface RFC, annotated accordingly.

Every new field gets range validation (following the existing
assertPositiveFinite pattern), a README row, and tests covering the
configured behavior, the schema default, and load-time rejection.

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

@@ -19,21 +19,22 @@
 import { FsError } from '@deepseek-ai/dsh-fs'
 import type { FsVersion } from '@deepseek-ai/dsh-fs'
 
-/** Maximum characters returned for a single line. */
+/** Default maximum characters returned for a single line (the `readMaxLineLength` config). */
 export const READ_MAX_LINE_LENGTH = 2000
 
-/** Maximum bytes returned for selected file lines. */
+/** Default maximum bytes returned for selected file lines (the `readMaxBytes` config). */
 export const READ_MAX_BYTES = 50 * 1024
 
-const READ_MAX_LINE_SUFFIX = `... (line truncated to ${READ_MAX_LINE_LENGTH} chars)`
-const LINE_BUFFER_CAP = READ_MAX_LINE_LENGTH + 1
-
 /** Resolved read window. The consumer applies its defaults/caps before calling. */
 export interface ReadWindow {
   /** 1-based first line to return. */
   offset: number
   /** Maximum number of lines to return. */
   limit: number
+  /** Maximum characters returned for a single line; overflow is truncated with a suffix. */
+  maxLineLength: number
+  /** Maximum bytes of selected output; overflow stops the scan and marks `truncatedByBytes`. */
+  maxBytes: number
 }
 
 /** One line returned from a text file. */
@@ -82,8 +83,8 @@ function newAccumulator(): WindowAccumulator {
   return { lines: [], totalLines: 0, outputBytes: 0, truncatedByBytes: false, done: false }
 }
 
-function truncateLine(line: string): string {
-  return line.length > READ_MAX_LINE_LENGTH ? `${line.substring(0, READ_MAX_LINE_LENGTH)}${READ_MAX_LINE_SUFFIX}` : line
+function truncateLine(line: string, maxLineLength: number): string {
+  return line.length > maxLineLength ? `${line.substring(0, maxLineLength)}... (line truncated to ${maxLineLength} chars)` : line
 }
 
 function lineByteSize(line: string, currentLineCount: number): number {
@@ -94,9 +95,9 @@ function consumeLine(acc: WindowAccumulator, rawLine: string, request: ReadWindo
   acc.totalLines += 1
   if (acc.totalLines < request.offset || acc.lines.length >= request.limit) return
 
-  const text = truncateLine(rawLine)
+  const text = truncateLine(rawLine, request.maxLineLength)
   const bytes = lineByteSize(text, acc.lines.length)
-  if (acc.outputBytes + bytes > READ_MAX_BYTES) {
+  if (acc.outputBytes + bytes > request.maxBytes) {
     acc.truncatedByBytes = true
     acc.done = true
     return
@@ -121,7 +122,7 @@ function finish(acc: WindowAccumulator, request: ReadWindow, displayPath: string
  * Accepts an `AsyncIterable<string>` (a chunked `streamText`) or an
  * `Iterable<string>` (a whole-file `readText` wrapped as `[text]`), so one code
  * path serves both. Scans for newlines with a capped line buffer (a newline-free
- * giant line is truncated, never buffered past {@link READ_MAX_LINE_LENGTH}),
+ * giant line is truncated, never buffered past `request.maxLineLength`),
  * enforces the byte cap, and throws `FS_NOT_FOUND` for an offset past EOF.
  */
 export async function buildWindow(
@@ -130,12 +131,14 @@ export async function buildWindow(
   displayPath: string,
 ): Promise<WindowResult> {
   const acc = newAccumulator()
+  // One char past the truncation point is enough to prove a line overflows.
+  const lineBufferCap = request.maxLineLength + 1
   let lineBuffer = ''
 
   function appendToLineBuffer(segment: string): void {
-    if (lineBuffer.length >= LINE_BUFFER_CAP) return
+    if (lineBuffer.length >= lineBufferCap) return
     lineBuffer += segment
-    if (lineBuffer.length > LINE_BUFFER_CAP) lineBuffer = lineBuffer.slice(0, LINE_BUFFER_CAP)
+    if (lineBuffer.length > lineBufferCap) lineBuffer = lineBuffer.slice(0, lineBufferCap)
   }
 
   function flushLine(): void {