fix: keep customer content out of loguru message formatting during index retries

[phernandez]

Why

Index retry jobs can reach Loguru with customer-derived note paths already interpolated into the
message template. When a path contains literal braces such as {AG}, Loguru treats the customer
text as a formatting field and raises KeyError, preventing the note from indexing across every
identical job attempt.

Closes #1212

What Changed

• pass customer-derived paths as positional Loguru arguments in both per-file markdown retry loops
• apply the same brace-safe pattern to sibling regular-file and markdown debug log calls in the
  two audited indexing modules
• cover both reachable retry loops with real Loguru rendering and brace-bearing filename/title
  regressions

Implementation Details

The log messages now use static templates and provide paths as positional arguments, which Loguru
formats once without interpreting braces inside the argument value. Existing structured context
such as entity IDs, checksums, operations, and graph counts remains attached to each record. This
is intentionally a call-site fix rather than a logging wrapper or content sanitizer.

Testing

Automated

• uv run pytest tests/indexing/test_file_indexer.py tests/index/test_local_markdown_file_indexer.py -q: 12 passed
• just fast-check: passed (Ruff fix/format and ty typecheck)
• just fast-test: 5,116 passed, 41 skipped
• just doctor: passed

Manual

• reproduced the pre-fix distinction directly with Loguru: positional notes/{AG}.md rendered,
  while the interpolated success template raised KeyError: 'AG'
• audited both changed modules and confirmed no Loguru call still uses an f-string template

Risks / Follow-ups

The change affects logging argument construction only; indexing control flow and persisted data are
unchanged. Production should be monitored for recurrence of the two Logfire issue cohorts cited in
#1212 after deployment.