refactor: trivial removals and deprecation completions

[devin-ai-integration]

Reference Issues/PRs

What does this implement or fix?

Five self-contained cleanup tasks:

1. Remove opt_false utility (cpp/arcticdb/util/optional_defaults.hpp)

   • Inlined the expression opt && *opt at all 8 call sites across version_core.cpp, version_store_api.cpp, local_versioned_engine.cpp, and read_options.hpp
   • Deleted the header file, removed #include from all consumers, removed from CMakeLists.txt

2. Deprecate is_symbol_fragmented (_store.py + library.py)

   • Added warnings.warn(..., DeprecationWarning) to both NativeVersionStore.is_symbol_fragmented and Library.is_symbol_fragmented
   • Added .. deprecated:: directive to docstrings directing users to defragment_symbol_data

3. Remove iterate_on_failure parameter (_store.py)

   • Removed the deprecated no-op parameter from list_versions and has_symbol signatures, docstrings, and warning logic
   • Removed stale @param iterate_on_failure comment in version_map.hpp

4. Remove force_uri_lib_config field (s3_library_adapter.py)

   • Removed the field from the ParsedQuery dataclass
   • Moved backward-compatibility handling into _parse_query: force_uri_lib_config=true is silently ignored, force_uri_lib_config=false still raises ValueError

5. Update BACKUP_SNAPSHOT_REF comment (key.hpp)

   • Confirmed no write paths use this key type (only enum definition, pybind11 binding, and key serialization)
   • Replaced misleading "Temporary - remove_me" comment with documentation that the value is retained for backward compatibility since KeyType enum values are persisted to storage

API changes

• NativeVersionStore.list_versions: Removed iterate_on_failure parameter (was deprecated, no-op)
• NativeVersionStore.has_symbol: Removed iterate_on_failure parameter (was deprecated, no-op)
• NativeVersionStore.is_symbol_fragmented: Now emits DeprecationWarning
• Library.is_symbol_fragmented: Now emits DeprecationWarning
• ParsedQuery.force_uri_lib_config: Field removed from dataclass; URI parameter still accepted for backward compatibility

Any other comments?

All changes are low-risk and self-contained. No on-disk format changes. BACKUP_SNAPSHOT_REF enum value (= 20) is intentionally kept to preserve storage compatibility.

Checklist

Checklist for code changes...

• Have you updated the relevant docstrings, documentation and copyright notice?
• Is this contribution tested against all ArcticDB's features?
• Do all exceptions introduced raise appropriate error messages?
• Are API changes highlighted in the PR description?
• Is the PR labelled as enhancement or bug so it appears in autogenerated release notes?

Link to Devin session: https://app.devin.ai/sessions/ada4efc2f8bf434fbdc84f6fc291b2a5
Requested by: @chrischappell-cog

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✅ Devin Review: No Issues Found

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Test Results

Tested Python changes against pip-installed arcticdb (v6.13.0) with branch Python files overlaid, using local LMDB backend.

Task 1 — iterate_on_failure removal (2/2 passed)

• NativeVersionStore.list_versions(iterate_on_failure=True) → TypeError: got an unexpected keyword argument 'iterate_on_failure' ✓
• NativeVersionStore.has_symbol(iterate_on_failure=True) → TypeError: got an unexpected keyword argument 'iterate_on_failure' ✓

Task 2 — is_symbol_fragmented deprecation (2/2 passed)

• NativeVersionStore.is_symbol_fragmented("sym") → emits DeprecationWarning with message "is_symbol_fragmented is deprecated. Use defragment_symbol_data instead..." ✓
• Library.is_symbol_fragmented("sym") → emits DeprecationWarning with same message ✓
• Both methods still return bool as expected ✓

Task 3 — force_uri_lib_config removal (4/4 passed)

• force_uri_lib_config removed from ParsedQuery dataclass fields ✓
• _parse_query("?force_uri_lib_config=true") → silently returns ParsedQuery (backward compat) ✓
• _parse_query("?force_uri_lib_config=false") → ValueError with security concerns message ✓
• Invalid params (e.g. ?bogus_param=true) still correctly rejected ✓

Regression — list_versions / has_symbol integration (4/4 passed)

• NativeVersionStore.list_versions("sym") → returns correct version data (symbol="sym", version=0, deleted=False) ✓
• NativeVersionStore.has_symbol("sym") → True ✓
• NativeVersionStore.has_symbol("nonexistent") → False ✓
• Library.has_symbol → works correctly ✓

Not tested (requires full C++ build)

• opt_false inlining (Task 1): Verified by code inspection — opt && *opt is semantically identical
• BACKUP_SNAPSHOT_REF comment (Task 5): Comment-only, no behavioral change

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