feat: bash-backed glob/grep discovery tools (dsh-tool-fs-search)

Implements docs/rfc/implemented/feature/2026-07-09-bash-backed-grep-glob-
discovery.md: model-facing glob/grep in a new @deepseek-ai/dsh-tool-fs-search
package, executing fixed ripgrep templates through ctx.bash.resolve/run —
not ctx.fs provider methods — so filesystem backends stay free of a search
contract and sandboxed/remote executors substitute cleanly. The tools never
call ctx.bash.start(); the tool layer owns quoting (one singleQuote safety
boundary), rg --json parsing, ItemRetainer/TextRetainer retention, and the
first tool-owned ctx.spillFiles.saveText() handoff (item-level retention the
generic post-execute spill policy cannot recover).

RFC amendments on the way to implemented/: a shared src/search-core.ts (the
SEARCH_* vocabulary + bash-run/raw-spill/spill plumbing was byte-identical
across both tools — the missed-extraction smell), and a snapshot-gap note:
wiring the acp-agent tree changes the assembled prompt, so goldens need a
keyed re-record; the spill notice text is pinned by unit tests instead and
only the coding-agent example ships the tools for now.

docs/config-catalog.md

@@ -724,6 +724,28 @@ export interface Config {
 
 Source: [`packages/fs/tool-fs/src/index.ts:48`](../packages/fs/tool-fs/src/index.ts)
 
+## `@deepseek-ai/dsh-tool-fs-search`
+
+Requires: `tools` · `systemPrompt` · `bash`
+
+```ts config-catalog
+/** Plugin config (all optional — `Config` supplies the defaults). */
+export interface Config {
+  /** Max paths one `glob` call retains inline; later paths go to the formatted spill file. */
+  globMaxResults?: number
+  /** Max flat matches one `grep` call retains inline; later matches go to the formatted spill file. */
+  grepMaxMatches?: number
+  /** Max bytes retained for one matched-line preview (the cut preserves UTF-8 boundaries). */
+  grepMaxLineBytes?: number
+  /** Max complete raw `rg` stdout bytes a search will parse; larger raw output fails with `SEARCH_RAW_OUTPUT_OVERFLOW`. */
+  rawOutputMaxBytes?: number
+  /** Cooperative tool-call timeout budget (ms) on both tools, enforced by `@deepseek-ai/dsh-timeout-policy` through `exec.signal`. */
+  timeoutMs?: number
+}
+```
+
+Source: [`packages/fs/tool-fs-search/src/index.ts:59`](../packages/fs/tool-fs-search/src/index.ts)
+
 ## `@deepseek-ai/dsh-tool-subagent`
 
 Requires: `tools` · `subagents`