v1.13.15-tools: tiered tool loading via BOOCODE_TOOLS env var

Pattern lift from eyaltoledano/claude-task-master (MIT + Commons Clause
— pattern only, no code lift). Adds BOOCODE_TOOLS env var with three
tiers:

- core (4 tools): view_file, list_dir, grep, find_files. ~2k token
  schema cost.
- standard (15 tools): core + web_search, web_fetch, git_status, all
  8 codecontext_* tools. ~10k token schema cost.
- all (default; current behavior): every tool in ALL_TOOLS (20). ~21k
  token schema cost.

The env var is a CEILING — narrows agent whitelists, never expands.
Default behavior unchanged when var is unset. resolveToolTier is
case-insensitive and falls back to 'all' on unknown values.

CORE_TOOL_NAMES + STANDARD_TOOL_NAMES validated at module load against
TOOLS_BY_NAME via two top-level for-loops that throw on the first
missing name. Module fails to import if a tier references a tool that
doesn't exist in the registry — catches typos and stale tier
definitions at boot rather than silently filtering valid tools out of
agent whitelists.

Wiring: agents.ts parseAgentBlock now reads BOOCODE_TOOLS from
process.env per parse, intersects with the agent's declared frontmatter
tools (or DEFAULT_TOOLS when frontmatter omits the field). Per-parse
read is fine — agents are re-parsed on the existing 60s cache TTL.

Tests: tools.test.ts grows from 1 to 10 tests. Covers resolveToolTier
across tiers/case/unknown values + the CORE-subset-of-STANDARD invariant
+ TOOLS_BY_NAME existence for both tier sets. 204/204 pass (was 195;
+9 new).

Deviation from the brief: the codecontext tools in the actual registry
have NO codecontext_* prefix (the brief's STANDARD list assumed it).
Used the actual names (get_codebase_overview, search_symbols, etc.).
Module-load validation would have failed boot with the prefixed names.

Smoke: with BOOCODE_TOOLS unset, agents return their full 12-tool
whitelists. With BOOCODE_TOOLS=core in .env + container restart, the
same agents narrow to 4 tools (find_files, grep, list_dir, view_file)
— intersection of declared whitelist ∩ core tier. Reverted after
confirmation.

CLAUDE.md updated with BOOCODE_TOOLS in the Environment section's
Optional list. .env.example gained a commented BOOCODE_TOOLS=all line
with the per-tier token-cost table.

~110 LoC across 5 files (4 modified + 1 test expansion). Under the
brief's ~30 LoC estimate for code; the test suite expansion drove
most of the growth.

apps/server/src/services/agents.ts

@@ -1,7 +1,7 @@
 import { promises as fs } from 'node:fs';
 import { join } from 'node:path';
 import type { Agent, AgentsResponse, AgentParseError } from '../types/api.js';
-import { ALL_TOOLS } from './tools.js';
+import { ALL_TOOLS, resolveToolTier } from './tools.js';
 
 // v1.8.1: global agents live at /data/AGENTS.md inside the container
 // (./data:/data:ro mount on the host). Per-project AGENTS.md at the project
@@ -186,11 +186,14 @@ function parseAgentSection(section: RawSection): Omit<Agent, 'source'> {
     throw new Error(fmErrors.join('; '));
   }
 
+  // v1.13.15-tools: intersect with BOOCODE_TOOLS tier (ceiling, not expansion).
+  // Unset → resolveToolTier returns ALL tool names → no narrowing.
+  const tierAllowed = new Set(resolveToolTier(process.env.BOOCODE_TOOLS));
   const filteredTools = Array.isArray(fm.tools)
     ? fm.tools.filter((t): t is string =>
-        (ALL_TOOL_NAMES as readonly string[]).includes(t),
+        (ALL_TOOL_NAMES as readonly string[]).includes(t) && tierAllowed.has(t),
       )
-    : DEFAULT_TOOLS;
+    : DEFAULT_TOOLS.filter((t) => tierAllowed.has(t));
 
   return {
     id: slugify(section.name),