fix(graph): scope file history to its graph and un-dead-end under --all

[greenbugx]

Summary

Related Issue

Closes #

Type of Change

• feat — new feature
• fix — bug fix
• docs — documentation only
• refactor — no change in behavior
• test — tests only
• chore / ci — tooling, dependencies, workflows
• Breaking change — an existing keybinding, CLI flag, or output changes meaning

How This Was Tested

• Automated:
• By hand:
• Tested on: OS [e.g. Windows 11 / Ubuntu 24.04 / macOS 15], terminal [e.g. Windows Terminal / Alacritty / Kitty]

Screenshots / Recordings

Checklist

• cargo fmt — CI runs cargo fmt --check
• cargo clippy --all-targets -- -D warnings is clean, unused imports included
• cargo test passes
• Commits follow Conventional Commits
• Files are LF, not CRLF
• Nothing used that is newer than the rust-version floor in Cargo.toml
• A new module is listed in CONTRIBUTING.md's architecture overview

• New keybinding added to ui::help::SECTIONS, to the key list in its test, and to the README table

Notes for the Reviewer