refactor: isolate TUI inspector state

[mohitranka]

Summary

• Group sidebar visibility and inspector-tab selection into InspectorState.
• Preserve focus availability, rendering, and inspector navigation behavior.

Validation

• cargo fmt --all -- --check
• cargo test -p forge-tui --lib --locked (683 passed)
• cargo clippy -p forge-tui --all-targets --locked -- -D warnings
• git diff --check

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Review details

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Configuration used: defaults

Review profile: CHILL

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Run ID: dd3be88c-f0eb-4899-acdf-bf55683cf47e

📥 Commits

Reviewing files that changed from the base of the PR and between 839c7d6 and 4e50bfb.

📒 Files selected for processing (8)

• crates/forge-tui/src/app/commands.rs
• crates/forge-tui/src/app/focus.rs
• crates/forge-tui/src/app/new.rs
• crates/forge-tui/src/app/render.rs
• crates/forge-tui/src/app/tests/chrome.rs
• crates/forge-tui/src/app/tests/commands.rs
• crates/forge-tui/src/app/tests/focus.rs
• crates/forge-tui/src/app/types.inc.rs

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