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/web/tool-web/src/index.ts

@@ -20,7 +20,7 @@
 import type { Context } from 'cordis'
 import z from 'schemastery'
 import type {} from '@deepseek-ai/dsh-web'
-import { applyWebSearchTool } from './search.ts'
+import { applyWebSearchTool, WEB_SEARCH_MAX_RESULTS } from './search.ts'
 import { applyWebFetchTool } from './fetch.ts'
 
 export { WEB_SEARCH_MAX_RESULTS, applyWebSearchTool, formatSearchOutput, parseSearchArgs, presentSearchCall } from './search.ts'
@@ -38,13 +38,26 @@ export interface Config {
   search?: boolean
   /** Register `web_fetch`. Defaults to true. */
   fetch?: boolean
+  /** Upper bound on sources returned by one `web_search` call. */
+  searchMaxResults?: number
 }
 
 export const Config: z<Config> = z.object({
   search: z.boolean().default(true),
   fetch: z.boolean().default(true),
+  searchMaxResults: z.number().default(WEB_SEARCH_MAX_RESULTS),
 })
 
+/** The shape after schemastery applies its defaults to every field. */
+type ResolvedConfig = Required<Config>
+
+/** The result cap must be a positive integer (it bounds a provider's source list). */
+function assertPositiveInteger(name: string, value: number): void {
+  if (!Number.isInteger(value) || value < 1) {
+    throw new Error(`tool-web: ${name} must be a positive integer`)
+  }
+}
+
 /**
  * Register the enabled web tools. `search`/`fetch` default to true; a product
  * that wants only one disables the other in config. The tools' disposers are
@@ -52,6 +65,9 @@ export const Config: z<Config> = z.object({
  * teardown is needed.
  */
 export function apply(ctx: Context, config: Config): void {
-  if (config.search !== false) applyWebSearchTool(ctx)
-  if (config.fetch !== false) applyWebFetchTool(ctx)
+  // schemastery (Config) has already filled every defaulted field.
+  const resolved = config as ResolvedConfig
+  assertPositiveInteger('searchMaxResults', resolved.searchMaxResults)
+  if (resolved.search) applyWebSearchTool(ctx, resolved.searchMaxResults)
+  if (resolved.fetch) applyWebFetchTool(ctx)
 }