Make the component library a standalone product door (2.63.0).

Add /api/library datasheet import and component GET/PUT with no exam.
Reorganize pytest into datasheet, library, schematic, PCB, and AF+AI.
Document Rust criteria (none chosen; no rustup) and coding conformity.

tests/datasheet/test_cache_breakpoint_limit.py

@@ -0,0 +1,81 @@
+"""Tests for the Anthropic cache_control breakpoint cap.
+
+Anthropic rejects requests with >4 cache_control blocks. The review path adds
+one per cacheable PDF excerpt, so a hub IC fetching two interface excerpts hit
+5 (system + initial PDF + initial context + 2 excerpts) and the API returned
+"A maximum of 4 blocks with cache_control may be provided. Found 5." The
+provider caps message-block breakpoints so system(1) + messages never exceed 4.
+"""
+
+from __future__ import annotations
+
+from backend.services.llm.anthropic_provider import _enforce_cache_breakpoint_limit
+
+
+def _cc(block: dict) -> bool:
+    return "cache_control" in block
+
+
+def _count(messages: list[dict]) -> int:
+    return sum(_cc(b) for m in messages for b in m["content"])
+
+
+def _ephemeral() -> dict:
+    return {"cache_control": {"type": "ephemeral"}}
+
+
+def test_u2_two_excerpts_capped_to_three():
+    """The exact failure: initial PDF + context + 2 excerpts = 4 message
+    breakpoints (5 with system). Cap to 3 so the total lands at 4."""
+    initial_pdf = {"type": "document", "source": {}, **_ephemeral()}
+    initial_text = {"type": "text", "text": "ctx", **_ephemeral()}
+    excerpt1 = {"type": "document", "source": {}, **_ephemeral()}
+    excerpt2 = {"type": "document", "source": {}, **_ephemeral()}
+    messages = [
+        {"role": "user", "content": [initial_pdf, initial_text]},
+        {"role": "assistant", "content": [{"type": "tool_use", "id": "a", "name": "x", "input": {}}]},
+        {"role": "user", "content": [{"type": "tool_result", "tool_use_id": "a", "content": "."}, excerpt1]},
+        {"role": "assistant", "content": [{"type": "tool_use", "id": "b", "name": "x", "input": {}}]},
+        {"role": "user", "content": [{"type": "tool_result", "tool_use_id": "b", "content": "."}, excerpt2]},
+    ]
+
+    _enforce_cache_breakpoint_limit(messages)
+
+    assert _count(messages) == 3  # +1 system = 4 total, within the limit
+    # The stable full-datasheet anchor and the two most recent excerpts survive;
+    # the initial context block (cheap to reprocess) loses its breakpoint.
+    assert _cc(initial_pdf)
+    assert not _cc(initial_text)
+    assert _cc(excerpt1)
+    assert _cc(excerpt2)
+
+
+def test_heavy_fanout_keeps_anchor_and_tail():
+    """A heavy-fanout review (many excerpts) still caps to 3 and always keeps
+    the first cacheable block (the full-datasheet anchor)."""
+    anchor = {"type": "document", "source": {}, **_ephemeral()}
+    messages = [{"role": "user", "content": [anchor, {"type": "text", "text": "x", **_ephemeral()}]}]
+    excerpts = []
+    for _ in range(6):
+        ex = {"type": "document", "source": {}, **_ephemeral()}
+        excerpts.append(ex)
+        messages.append({"role": "user", "content": [ex]})
+
+    _enforce_cache_breakpoint_limit(messages)
+
+    assert _count(messages) == 3
+    assert _cc(anchor)
+    # Two most-recent excerpts retained for incremental tail caching.
+    assert _cc(excerpts[-1]) and _cc(excerpts[-2])
+
+
+def test_under_limit_untouched():
+    """Three or fewer message breakpoints are left exactly as-is."""
+    pdf = {"type": "document", "source": {}, **_ephemeral()}
+    text = {"type": "text", "text": "x", **_ephemeral()}
+    messages = [{"role": "user", "content": [pdf, text]}]
+
+    _enforce_cache_breakpoint_limit(messages)
+
+    assert _cc(pdf) and _cc(text)
+    assert _count(messages) == 2