fix(bedrock): raise Claude 4.x context window to 1M and add opus-4-7

Claude 4.x models on Bedrock support a 1M-token context window via the
context-1m-2025-08-07 beta header, which Hermes already injects
automatically in build_anthropic_bedrock_client
(agent/anthropic_adapter.py). However, BEDROCK_CONTEXT_LENGTHS in
agent/bedrock_adapter.py still reported 200K for opus-4-6, sonnet-4-6,
sonnet-4-5, and haiku-4-5, and had no entry at all for opus-4-7 (which
falls back via substring match to the 200K opus-4 entry).

This caused Hermes to display a 200K window, compress conversations
earlier than necessary (compression.threshold * 200K instead of * 1M),
and generally under-utilize the full 1M context users are paying for.

The fix is metadata-only — the Bedrock API and beta header already
support 1M end-to-end. agent/model_metadata.py's DEFAULT_CONTEXT_LENGTHS
table already lists claude-opus-4-7 / -4-6 / sonnet-4-6 at 1M for the
non-Bedrock paths, so this change brings the Bedrock table into
alignment.

Changes:
- Add anthropic.claude-opus-4-7 at 1_000_000
- Bump anthropic.claude-opus-4-6 from 200_000 to 1_000_000
- Bump anthropic.claude-sonnet-4-6 from 200_000 to 1_000_000
- Bump anthropic.claude-sonnet-4-5 from 200_000 to 1_000_000
- Bump anthropic.claude-haiku-4-5 from 200_000 to 1_000_000
- Add explanatory comment pointing readers at the beta-header injection
  site in agent/anthropic_adapter.py

agent/bedrock_adapter.py

@@ -1321,12 +1321,16 @@ def classify_bedrock_error(error_message: str) -> str:
 # detection is unavailable.
 
 BEDROCK_CONTEXT_LENGTHS: Dict[str, int] = {
-    # Anthropic Claude models on Bedrock
+    # Anthropic Claude models on Bedrock.
+    # Claude 4.x (opus/sonnet/haiku) support a 1M-token context window via the
+    # ``context-1m-2025-08-07`` beta header, which Hermes injects automatically
+    # in ``build_anthropic_bedrock_client`` (see agent/anthropic_adapter.py).
     "anthropic.claude-sonnet-5":     1_000_000,
-    "anthropic.claude-opus-4-6":     200_000,
-    "anthropic.claude-sonnet-4-6":   200_000,
-    "anthropic.claude-sonnet-4-5":   200_000,
-    "anthropic.claude-haiku-4-5":    200_000,
+    "anthropic.claude-opus-4-7":     1_000_000,
+    "anthropic.claude-opus-4-6":     1_000_000,
+    "anthropic.claude-sonnet-4-6":   1_000_000,
+    "anthropic.claude-sonnet-4-5":   1_000_000,
+    "anthropic.claude-haiku-4-5":    1_000_000,
     "anthropic.claude-opus-4":       200_000,
     "anthropic.claude-sonnet-4":     200_000,
     "anthropic.claude-3-5-sonnet":   200_000,