fix(cli): tab-complete paths with embedded spaces

[0xDevNinja]

What does this PR do?

_extract_path_word() in hermes_cli/commands.py walked back to the
nearest space, so after prompt_toolkit autocompleted a directory whose
name contained a space (e.g. ./My Documents/), pressing Tab again
extracted just Documents/. That isn't a directory in cwd, so the
listdir returned nothing and tab completion silently stopped working
for everything inside that directory.

Fix

Find the rightmost anchored prefix (./, ../, ~/, /) that sits
at the start of the line or directly after a space, and treat
everything from there to the cursor as the path. When no anchor is
present, fall back to the last space-delimited token (preserves the
existing mid-line open src/utils/x.py behaviour).

Why not the heuristic proposed in the issue body

The "keep walking past a space if the tail contains a slash" rule
over-consumes in normal prose — for tell me about ./My Documents/,
every backwards chunk contains a slash, so the walk reaches the start
of the line and the resulting "word" can never be listdir'd. The
anchor-based approach stops as soon as the captured tail can stand on
its own as a path.

Related Issue

Fixes #26223

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature
• Breaking change
• Documentation update
• Code refactor / cleanup
• Performance improvement
• Test coverage improvement

Changes Made

• hermes_cli/commands.py — anchor-based _extract_path_word().
• tests/hermes_cli/test_path_completion.py — six new cases covering
  ./My Documents/, mid-sentence look at ./My Documents/, /etc/My Files/, ~/My Notes/todo.md, deep ./My Documents/Sub Folder/file.py,
  and the anchored-extension fallback for ./src/foo bar.py.

Testing

uv run pytest tests/hermes_cli/test_path_completion.py -q
# 33 passed

[alt-glitch]

Likely duplicate of #26230 — both fix _extract_path_word() space handling for #26223. This PR uses an anchor-based approach vs #26230's approach. Maintainer should pick one and close the other.