feat: Add in-TUI log panel to prevent log messages from breaking layout

[inureyes]

Summary

• Adds a dedicated log panel within the TUI interface to capture and display tracing events (ERROR, WARN, INFO, DEBUG) without breaking the ratatui alternate screen layout
• Implements LogBuffer and LogEntry structs for in-memory log storage with configurable max entries (default 1000)
• Implements TuiLogLayer that captures tracing events and stores them in the shared buffer
• Adds log panel view component with color-coded output by log level

Key Features

• Log Buffer: Configurable max entries via BSSH_TUI_LOG_MAX_ENTRIES environment variable
• Color-coded levels: ERROR=red, WARN=yellow, INFO=white, DEBUG=gray
• Keyboard shortcuts:
  • l - Toggle log panel visibility
  • j/k - Scroll logs when panel is visible
  • +/- - Resize panel (3-10 lines)
  • t - Toggle timestamps
• Auto-refresh: Detects new log entries and triggers redraw

Files Changed

New Files

• src/ui/tui/log_buffer.rs - LogBuffer and LogEntry structs
• src/ui/tui/log_layer.rs - TuiLogLayer implementing tracing_subscriber::Layer
• src/ui/tui/views/log_panel.rs - Log panel view component

Modified Files

• src/ui/tui/app.rs - Added log panel state fields and methods
• src/ui/tui/event.rs - Added key bindings for log panel controls
• src/ui/tui/mod.rs - Integrated log layer and panel rendering
• src/ui/tui/views/*.rs - Added render_in_area() for layout flexibility
• src/utils/logging.rs - Extracted filter creation for reuse
• tests/tui_snapshot_tests.rs - Updated assertion for new footer layout

Test Plan

• All existing tests pass (638 tests)
• Clippy check passes with no warnings
• Code formatted with rustfmt
• Manual testing: verify log panel displays correctly
• Manual testing: verify keyboard shortcuts work
• Manual testing: verify logs are captured without breaking TUI

Fixes #104

[inureyes]

Security & Performance Review

Analysis Summary

• Scope: changed-files
• Languages: Rust
• Total changed files: 13
• Total additions: 1147 lines
• Total deletions: 22 lines
• Tests: All 638 tests pass
• Clippy: No warnings

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Prioritized Issue Roadmap

CRITICAL Issues: 0

No critical security vulnerabilities identified.

HIGH Issues: 0

No high-severity issues identified.

MEDIUM Issues: 3

#	Issue	File	Lines
1	Mutex lock held during formatting operations	src/ui/tui/views/log_panel.rs	85-137
2	Lock contention between tracing layer and UI	src/ui/tui/log_layer.rs	119-121
3	Env var parsing without upper bound validation	src/ui/tui/log_buffer.rs	117-121

LOW Issues: 5

#	Issue	File
4	Unnecessary clone in log entry rendering	views/log_panel.rs:117
5	Redundant rsplit calls for module name	Multiple files
6	Magic numbers lack documentation	views/log_panel.rs:32-38
7	Scroll HashMap eviction not LRU (acceptable)	app.rs:192-207
8	Silent mutex poisoning handling	Multiple files

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Positive Observations

• Thread-safe design with Arc<Mutex<LogBuffer>>
• Bounded buffer with FIFO eviction prevents memory exhaustion
• RAII TerminalGuard ensures proper cleanup
• Comprehensive test coverage (324 lines of new tests)
• Proper scroll position bounds checking throughout
• No security vulnerabilities detected

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Summary

Category	Count
CRITICAL	0
HIGH	0
MEDIUM	3
LOW	5

Overall Assessment: This PR is safe to merge. All identified issues are quality/performance improvements rather than blocking concerns. The code demonstrates good Rust practices.

Recommendation: Consider addressing MEDIUM issues in a follow-up PR if high logging volume is expected in production use.

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Review completed by Claude Code security review assistant