Fix right loop panel

[coneilen]

Summary

Fix the right loop panel so text bounds come from the panel/container instead of a fixed canvas edge, and reshape the panel toward the macOS reference with a THIS LOOP minimap and a HANDS OFF TO list.

Changes

• Replaced the fixed 1200px text bound in GraphCanvas.zig with container-derived text bounds.
• Updated the canvas text callers on the loop cards, attention rail, activity strip, lane cards, and loop detail rail to use container-limited drawing.
• Restructured the loop detail rail toward the macOS reference with THIS LOOP, HANDS OFF TO, and a started <time> footer.
• Added geometry tests for bounded text rectangles, loop detail row layout, and minimap overlap.

Test plan

RED: zig test src\GraphCanvas.red.zig --test-filter "bounded text rectangles" -target x86_64-windows-msvc -lc "-IC:\gcp\b\winghostty\include" --cache-dir C:\gcs\b\cache --global-cache-dir C:\gcs\b\global -> throwaway GraphCanvas.red.zig snapshot reproduces the fixed 1200px text edge; expected 1762, found 1200
GREEN: zig test src\GraphCanvas.zig -target x86_64-windows-msvc -lc "-IC:\gcp\b\winghostty\include" --cache-dir C:\gcs\b\zig-cache --global-cache-dir C:\gcs\b\zig-global -> All 219 tests passed.
REGRESSION: pwsh -NoProfile -File Tools\windows\validate.ps1 -Task windows-shell -ShellPart unit -SkipTrayLive -ShellValidationRoot C:\gc-b -SwiftExecutable C:\Users\coneilen\AppData\Local\Programs\Swift\Toolchains\6.3.3+Asserts\usr\bin\swift.exe -> All 167 tests passed; WINDOWS_SHELL_DEFAULT_PROFILE_UNCHANGED=verified; GDIPLUS_STARTUP_LIVE: PASS

Not verified

• Local integration hit Tools\windows\Tests\ScrubbedShellStartup.Live.Tests.ps1:250 with registered-project did not show the registered daemon project row; exact-head CI on this PR passed that gate, including registered-project and the UIA live gate, so this local failure is being treated as a local-environment issue.
• Local visual capture failed twice: first on a fixture-project deadline, then with Unable to start graphcoded.exe; I did not get usable before/after screenshots from this machine.
• Tools\windows\validate.ps1 -Task windows-shell -ShellPart integration -SkipTrayLive still needs the desktop lease for the live smoke, tray, and UI Automation checks if we want a local rerun.
• RED was captured from a throwaway GraphCanvas.red.zig snapshot that restores the original fixed 1200px text edge.

Checklist

• I have read the Contributing Guidelines
• I have signed off my commits (git commit -s) per the DCO
• Tests pass locally (make test)
• Code follows the existing style (make check)
• I captured the intended RED failure in a throwaway GraphCanvas.red.zig snapshot before keeping the implementation

[coneilen]

Superseded: #773 was escalated from gpt-5.4-mini to gpt-6.1-sol under the orchestration plan's 90-minute rule (handoff on #773). Commits f94ced6 and 874acc7 are kept on branch coneilen-microsoft-fix-right-loop-panel-wip, for the new session to cherry-pick.