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/index.ts

@@ -23,11 +23,14 @@
  */
 
 import type { Context } from 'cordis'
-import { applyReadTool } from './read.ts'
+import z from 'schemastery'
+import { applyReadTool, READ_LIMIT, STREAM_MIN_SIZE } from './read.ts'
 import { applyWriteTool } from './write.ts'
 import { applyEditTool } from './edit.ts'
+import { READ_MAX_BYTES, READ_MAX_LINE_LENGTH } from './read-render.ts'
 
 export { READ_LIMIT, STREAM_MIN_SIZE, applyReadTool, parseReadArgs } from './read.ts'
+export type { ReadToolCaps } from './read.ts'
 export { applyWriteTool, formatWriteOutput, parseWriteArgs } from './write.ts'
 export { applyEditTool, formatEditOutput, parseEditArgs } from './edit.ts'
 export { READ_MAX_BYTES, READ_MAX_LINE_LENGTH, buildWindow, formatReadOutput } from './read-render.ts'
@@ -41,9 +44,49 @@ export const name = 'tool-fs'
 /** Services required by the filesystem tool suite. */
 export const inject = ['tools', 'fs', 'systemPrompt']
 
+/** Plugin config (all optional — `Config` supplies the defaults). */
+export interface Config {
+  /** Default and maximum number of lines returned by one `read` call. */
+  readLimit?: number
+  /** Maximum characters returned for a single line before truncation. */
+  readMaxLineLength?: number
+  /** Maximum bytes returned for the selected lines of one `read` call. */
+  readMaxBytes?: number
+  /** Files at or above this size stream instead of loading whole into memory. */
+  readStreamMinSize?: number
+}
+
+export const Config: z<Config> = z.object({
+  readLimit: z.number().default(READ_LIMIT),
+  readMaxLineLength: z.number().default(READ_MAX_LINE_LENGTH),
+  readMaxBytes: z.number().default(READ_MAX_BYTES),
+  readStreamMinSize: z.number().default(STREAM_MIN_SIZE),
+})
+
+/** The shape after schemastery applied the defaults. */
+type ResolvedConfig = Required<Config>
+
+/** A read cap must be a positive finite number to bound output and memory. */
+function assertPositiveFinite(name: string, value: number): void {
+  if (!Number.isFinite(value) || value <= 0) {
+    throw new Error(`tool-fs: ${name} must be a positive finite number`)
+  }
+}
+
 /** Register the full `read`/`write`/`edit` filesystem tool suite. */
-export function apply(ctx: Context): void {
-  applyReadTool(ctx)
+export function apply(ctx: Context, config: Config): void {
+  // schemastery (Config) has already filled every defaulted field.
+  const resolved = config as ResolvedConfig
+  assertPositiveFinite('readLimit', resolved.readLimit)
+  assertPositiveFinite('readMaxLineLength', resolved.readMaxLineLength)
+  assertPositiveFinite('readMaxBytes', resolved.readMaxBytes)
+  assertPositiveFinite('readStreamMinSize', resolved.readStreamMinSize)
+  applyReadTool(ctx, {
+    limit: resolved.readLimit,
+    maxLineLength: resolved.readMaxLineLength,
+    maxBytes: resolved.readMaxBytes,
+    streamMinSize: resolved.readStreamMinSize,
+  })
   applyWriteTool(ctx)
   applyEditTool(ctx)
 }