MAJOR: Duplicate PR conflict - both #987 and #988 modify identical code

[krystophny]

CRITICAL: Duplicate PR merge conflict requires immediate coordination

PROBLEM ANALYSIS:
Both PR #987 (PDF scaling) and PR #988 (marker visibility) modify identical coordinate transformation code in the PDF backend, creating merge conflicts.

EVIDENCE:

• PR fix: restore PDF plot scaling to fill available plot area (fixes #985) #987: Modifies PDF coordinate scaling and aspect ratio handling
• PR fix: restore PDF marker visibility by fixing coordinate transformation (fixes #986) #988: Modifies PDF coordinate transformation for marker positioning
• Conflict Zone: Both touch PDF coordinate transformation logic
• CI Status: Both PRs pass individually but will conflict on merge

TECHNICAL SOLUTION:

1. Merge PR fix: restore PDF plot scaling to fill available plot area (fixes #985) #987 first (PDF scaling foundation)
2. Rebase PR fix: restore PDF marker visibility by fixing coordinate transformation (fixes #986) #988 against updated main branch
3. Resolve conflicts by combining both coordinate fixes
4. Re-validate CI on rebased PR fix: restore PDF marker visibility by fixing coordinate transformation (fixes #986) #988

ARCHITECTURAL IMPACT:
Both fixes are complementary (scaling + markers) and should integrate without functional conflicts. The merge conflict is purely technical due to overlapping code regions.

RESOLUTION PROTOCOL:
max-devops-engineer must coordinate merge order and rebase operation to combine both critical regression fixes without losing either functionality.

PRIORITY: IMMEDIATE - Blocks Sprint #1 completion and Sprint #2 initiation