Use developerknowledge-go for documentation API

[apstndb]

Summary

• replace the local Developer Knowledge API HTTP/error/retry client with github.com/apstndb/developerknowledge-go v0.1.2
• use the GA v1 Developer Knowledge document endpoints while keeping spanner-mycli-specific document name normalization, search result formatting, and batch-to-individual fallback behavior
• update tests for the shared rate-limit error type while preserving the existing three total attempts

Tests

• make check

[gemini-code-assist]

Code Review

This pull request refactors the Developer Knowledge API client in internal/mycli/statements_llm_tooluse.go and its corresponding tests to use the external github.com/apstndb/developerknowledge-go library. This replaces custom HTTP client logic, rate limiting, retry mechanisms, and JSON unmarshaling with the library's client and types, significantly simplifying the codebase. There are no review comments to evaluate, and I have no additional feedback to provide.

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[github-actions]

Code Metrics Report

📊 View detailed coverage report (available for 7 days)

	main (576e32c)	#681 (070ab34)	+/-
Coverage	70.2%	70.2%	-0.1%
Code to Test Ratio	1:1.2	1:1.2	+0.0
Test Execution Time	1m42s	46s	-56s

Details

  |                     | main (576e32c) | #681 (070ab34) |  +/-  |
  |---------------------|----------------|----------------|-------|
- | Coverage            |          70.2% |          70.2% | -0.1% |
  |   Files             |             84 |             84 |     0 |
  |   Lines             |           7517 |           7480 |   -37 |
- |   Covered           |           5281 |           5253 |   -28 |
+ | Code to Test Ratio  |          1:1.2 |          1:1.2 |  +0.0 |
  |   Code              |          17283 |          17214 |   -69 |
+ |   Test              |          22323 |          22335 |   +12 |
+ | Test Execution Time |          1m42s |            46s |  -56s |

Code coverage of files in pull request scope (87.1% → 90.4%)

Files	Coverage	+/-	Status
internal/mycli/statements_llm_tooluse.go	90.4%	+3.3%	modified

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Reported by octocov