docs(oci-dac): tutorial 40 + empirical Qwen confirmation + website

[fede-kamel]

Follow-up to #24 (DAC support landed). This wires the full reader-facing story: tutorial, how-to update with empirical Qwen confirmation, README + homepage capability rows, and the bumped tutorial counter.

Tutorial 40 — examples/tutorial_40_oci_dac.py

Five-part walkthrough, live-tested against Luigi's London DAC:

1. Auto-routing — OCID prefix → SDK transport
2. Configure — pre-build via get_model() (strict AgentConfig)
3. complete() — single round-trip against the DAC
4. stream() — real SSE deltas
5. Agent + @tool — wiring + honest note on Qwen's <tool_call> text-block format

Live run output

Captured in the how-to page:

=== Part 3: complete() against the DAC ===
Reply:        'I am a large-scale language model developed by Alibaba Cloud, known as Qwen.'
usage:        {'prompt_tokens': 17, 'completion_tokens': 18}
stop_reason:  stop

=== Part 4: stream() against the DAC ===
Streaming reply (chunks shown inline):
  1, 2, 3, 4, 5

What's proven:

• Routing oci:ocid1.generativeaiendpoint.... → OCIModel ✓
• DedicatedServingMode(endpoint_id=...) accepted by the live endpoint ✓
• Real SSE — chunks arrive as character deltas, not the fallback path ✓
• Token accounting populated correctly ✓

What's flagged honestly:

• Qwen on this DAC emits tool calls as <tool_call>{...}</tool_call> text blocks, not OpenAI-style structured tool_calls. Two remediation paths (deploy-side flag or caller-side post-process) documented in the how-to.

Surface updates

• docs/how-to/oci-dac.md — new "Confirmed working — Qwen on a London DAC" section with the run output and the tool-call format note.
• README.md capability grid: new 🏗 OCI Dedicated AI Cluster row.
• README.md tutorials: counter 39 → 40, new OCI track row covering 29 + 40.
• docs/index.md capability grid: same DAC row added.
• docs/index.md tutorials: counter 39 → 40, tutorial 40 added to Track-5.

Validation

• 3205 unit tests pass, no regressions.
• hatch run check clean.
• Tutorial runs cleanly in mock mode (no env) and live mode (OCI_DAC_* env vars set).

Privacy

No tenancy / endpoint OCIDs in the codebase. The tutorial reads them from env vars; the how-to references only the region.