Move DIRECTORY.md to its own section in pr_file_map.py

[priya-sundaram-dev]

Describe your change

Per @cclauss's request in #15081, this reworks scripts/pr_file_map.py so that DIRECTORY.md no longer distracts busy maintainers.

DIRECTORY.md is auto-generated, so nearly every open PR modifies it. That meant it was always the single most "contested" file and dominated the possible merge conflicts list, drowning out the real source-file collisions maintainers actually need to coordinate.

Changes

• DIRECTORY.md gets its own section at the very bottom of the report, out of the contested/existing lists. Because a conflict caused only by this file is trivially resolved with accept both in the GitHub UI, that bottom section splits the PRs into:
  • PRs whose only overlap is DIRECTORY.md — safe to accept both, no rebase needed; and
  • PRs that also overlap on other files — these need a genuine review or rebase, with the specific conflicting files listed per PR.
• The "possible merge conflicts" count/list now excludes DIRECTORY.md, so it reflects only real source-file hot spots.
• The Script: line is now relative to the git root (scripts/pr_file_map.py) instead of an absolute, machine-specific path like /Users/cclauss/TheAlgorithms/Python/scripts/pr_file_map.py.
• Refactored the render into small helpers (split_directory_conflicts, render_file_section, render_directory_section) to keep main() under the McCabe/branch limits.

ruff check and ruff format --check are green, and I unit-tested the rendering against mocked gh data to confirm the categorization and the relative path.

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues, then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

[cclauss]

Love this!! Thx.