feat(adk): add read tool hint to truncation notice

[Zhang-986]

Summary

• add the configured read tool name to default truncation notices, matching clear-stage notices
• pass ReadFileToolName into the default truncation handler
• cover custom read tool names in default truncation output

Fixes #1110.

Tests

• go test ./adk/middlewares/reduction -run 'TestReductionMiddlewareTrunc/test_default_truncation_notice_includes_configured_read_tool_name' -count=1
• go test ./adk/middlewares/reduction -count=1
• go test ./adk/middlewares/reduction -coverprofile=/tmp/eino-reduction-1110.cover -covermode=count -count=1
• local patch coverage estimate: 100% (7/7 changed statements)
• go test ./adk/... -count=1
• git diff --check

[Slideee]

这个 PR 能合并吗

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.34%. Comparing base (747023b) to head (94d5bb2).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1118      +/-   ##
==========================================
+ Coverage   83.28%   83.34%   +0.06%     
==========================================
  Files         162      162              
  Lines       23397    23398       +1     
==========================================
+ Hits        19486    19501      +15     
+ Misses       2642     2629      -13     
+ Partials     1269     1268       -1     

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[N3kox]

@Zhang-986
Hi, please apply the modifications in this PR to the newly added prompts #1090 when you have time.

[Zhang-986]

Fixed in 94d5bb2.

Applied the read tool hint to the streaming offload-saved prompts introduced by #1090, covering both default streamable and enhanced streamable truncation paths. I kept the hint on the offload-saved notice so it is only shown when the full output was actually saved.

Verified:

• go test ./adk/middlewares/reduction -count=1
• go test ./adk/... -count=1
• git diff --check