fix: harden MCP statement output surface

[apstndb]

Summary

• Reject backslash meta commands from MCP execute_statement
• Cap MCP statement output capture and return an explicit truncation marker
• Route progress bars only to the StreamManager TTY, disabling them when no TTY is available
• Update MCP tool text to describe captured output rather than ASCII-only tables

Tests

• make check

[gemini-code-assist]

Code Review

This pull request introduces memory-safe output capturing and rejects backslash meta commands in the MCP execute_statement handler. Specifically, it adds an mcpOutputCapture helper to truncate output exceeding 1MB and updates the handler to reject meta commands like shell execution, output redirection, and teeing. Additionally, it refactors progress bar initialization to only instantiate when a TTY is available, preventing progress bar output from corrupting non-TTY streams (such as MCP). Comprehensive tests have been added to verify these behaviors. There are no review comments, so I have no feedback to provide.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.

[github-actions]

Code Metrics Report

📊 View detailed coverage report (available for 7 days)

	main (ec3190b)	#777 (aec0bd4)	+/-
Coverage	73.1%	73.1%	+0.0%
Code to Test Ratio	1:1.3	1:1.3	+0.0
Test Execution Time	1m39s	1m42s	+3s

Details

  |                     | main (ec3190b) | #777 (aec0bd4) |  +/-  |
  |---------------------|----------------|----------------|-------|
+ | Coverage            |          73.1% |          73.1% | +0.0% |
  |   Files             |             87 |             87 |     0 |
  |   Lines             |           7814 |           7840 |   +26 |
+ |   Covered           |           5715 |           5736 |   +21 |
+ | Code to Test Ratio  |          1:1.3 |          1:1.3 |  +0.0 |
  |   Code              |          18201 |          18256 |   +55 |
+ |   Test              |          24473 |          24564 |   +91 |
- | Test Execution Time |          1m39s |          1m42s |   +3s |

Code coverage of files in pull request scope (54.8% → 56.2%)

Files	Coverage	+/-	Status
internal/mycli/cli_mcp.go	83.0%	+5.8%	modified
internal/mycli/execute_ddl.go	41.9%	+1.0%	modified
internal/mycli/statements.go	56.9%	-0.2%	modified

---

Reported by octocov