Add Ruff rules B018 and UP034

[Abhayindia]

Summary of Changes

Bundles B018 and UP034 since the cleanup overlaps and you mentioned several rule issues can go in one PR.

B018 (useless-expression) turned up a real bug: MunichAdjustment.transform builds the ldf triangle but had obj._set_slicers without the call, so the returned triangle never rebuilt its .iloc/.loc/.at indexers after the shape change. The rest was test-side - a couple of dead lines, some smoke-check expressions bound to _, and the empty-triangle check in TriangleDisplay._dimensionality switched to hasattr instead of catching AttributeError on a bare self.values.

UP034 (extraneous-parentheses) was a few redundant paren pairs in clark.py, benktander.py and a couple of tests/notebooks.

Since touching a file drops its per-file-ignore protection, I cleaned each file I touched to the full ruleset and removed its entry: clark.py (also type(x) == -> isinstance and a stray assigned lambda -> def), display.py, test_bootstrap.py, test_munich.py. test_development.py, incremental.py, test_voting.py and two notebooks still trip one of the new rules but are big enough that a full cleanup belongs in its own PR, so they're grandfathered.

Related GitHub Issue(s)

Closes #1235
Closes #1236

Additional Context for Reviewers

ruff check + format with both rules is clean over the project apart from the grandfathered files. pytest passes for every touched module locally (234 tests). ruff format didn't touch any .. testcode:: block so the doctest build is unaffected.

[github-actions]

Pyright Type Completeness

View the full pyright --verifytypes output for this commit

Project (full chainladder package, at this PR's head): 15.2% of exported symbols fully typed (209 / 1377)

	Known	Ambiguous	Unknown	Total
Project (head)	209	111	1057	1377

Other symbols referenced but not exported by chainladder: 13

	Known	Ambiguous	Unknown	Total
Other (head)	3	1	9	13

Symbols without documentation:

• Functions without docstring: 325
• Functions without default param: 0
• Classes without docstring: 10

Patch (exported symbols added or changed by this PR): no exported symbol type-completeness changes detected.

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.70%. Comparing base (5f34bcd) to head (14bbc4d).

Files with missing lines	Patch %	Lines
chainladder/development/clark.py	77.77%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1243      +/-   ##
==========================================
- Coverage   91.70%   91.70%   -0.01%     
==========================================
  Files          93       93              
  Lines        5435     5434       -1     
  Branches      699      700       +1     
==========================================
- Hits         4984     4983       -1     
  Misses        327      327              
  Partials      124      124              

Flag	Coverage Δ
unittests	91.70% <90.90%> (-0.01%)	⬇️

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[henrydingliu]

looks good. please resolve conflict and i can approve

[Abhayindia]

rebased on main - the only conflict was in pyproject.toml (main dropped the base.py per-file-ignore, this PR drops clark.py's), resolved to drop both. ruff check + format clean on the changed files.