fix: rewrite download URL host to match HARNESS_BASE_URL for TLS compatibility

[mehulparmariitr]

Summary

• Fixes download_execution_logs TLS certificate errors when HARNESS_BASE_URL is set to a custom/vanity domain (e.g., mycompany.harness.io)
• Rewrites the pre-signed download URL host to match the configured base URL so it routes through the same trusted endpoint
• Uses the configured HTTP client (with its TLS transport) instead of bare http.Get() for the download request

Root Cause

The Harness /blob/download API returns pre-signed download URLs hardcoded to app.harness.io. When HARNESS_BASE_URL points to a different domain, the second HTTP call to app.harness.io fails because the corporate proxy/CA doesn't trust that certificate. Every other MCP tool works because they only make API calls to the configured base URL.

Changes

• common/client/logs.go — Added rewriteDownloadURLHost() to replace the download URL host/scheme with the configured BaseURL host. Falls back gracefully to the original URL if rewriting fails.
• common/client/client.go — Added HTTPClient() accessor to expose the underlying *http.Client so callers can share the same TLS/transport config without auth header injection.
• common/pkg/tools/logs.go — Added HTTPClient field to DownloadLogsConfig and replaced bare http.Get() with the configured client.
• common/client/logs_test.go — 5 test cases for URL rewriting (host rewrite, no-op when matching, nil base URL, query param preservation, path preservation).

Fixes #39

Test plan

• All existing tests pass (go test ./common/client/... ./common/pkg/tools/...)
• New unit tests for rewriteDownloadURLHost pass (5 cases)
• Manual test: set HARNESS_BASE_URL to a custom domain and verify download_execution_logs succeeds

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[mehulparmariitr]

When is this going to be merged @yogeshkc ?