v2.4.0-unsloth-studio-lift: port 3 Unsloth Studio AGPL-3.0 modules

Batch 1 — tool-call-parser.ts: replaces xml-parser.ts with a port of
Unsloth's tool_call_parser.py. Adds balanced-brace JSON scanner,
single-param fast path, hasToolSignal/stripToolMarkup/parseToolCallsFromText
exports, and stream-finalization stripping at all three final-write sites
(error-handler, finalizeCompletion, executeToolPhase). Anthropic <invoke>
shape preserved. 75+12 tests.

Batch 2 — web/html-to-md.ts: parse5 tree-walking HTML-to-Markdown converter
ported from Unsloth's _html_to_md.py. Replaces web_fetch's regex stripHtml
with structured markdown output (headings, links, lists, tables, code blocks,
blockquotes, entity decoding). 29 tests.

Batch 3 — llama-args-validator.ts: port of llama_server_args.py deny-list
validator. Wired into AGENTS.md frontmatter parser — llama_extra_args field
validated at load time, rejects managed flags (model identity, networking,
auth/TLS, server UI). No runtime consumer yet (llama-swap boundary). 76 tests.

All three files carry SPDX-License-Identifier: AGPL-3.0-only headers.
LICENSE flipped to AGPL-3.0-only in prior commit (a938cf1).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/server/src/services/inference/provider.ts

@@ -1,6 +1,9 @@
 import { createOpenAICompatible } from '@ai-sdk/openai-compatible';
 import type { LanguageModel } from 'ai';
 
+// TODO: When per-agent llama-server flag overrides are added, route them
+// through validateExtraArgs (./llama-args-validator.ts) first.
+
 // v1.13.1-A: AI SDK provider against llama-swap. baseURL is threaded from
 // config.LLAMA_SWAP_URL at call time (not module-load) so tests can stub the
 // upstream without touching env vars. No apiKey — llama-swap is unauth in our