fix(git): unify git_log output schema and remove raise_exceptions from server.run

[AbhiPra24]

Summary

Fixes #4469 and #4213.

1. Unified git_log Output Schema (Fixes #4469)

• Problem: The unfiltered git_log branch used !r formatting (commit.hexsha!r, commit.author!r, commit.message!r), which produced string representations with Python quotes, escaped newlines, and object repr (<git.Actor "Name <email>">). Meanwhile, the filtered branch used --format=%H%n%an%n%ad%n%s%n, which stripped commit bodies and output unquoted strings.
• Fix: Unified both branches with repo.iter_commits(), passing since/until filters when provided, preserving full multiline commit messages and consistent string outputs across both branches without !r quotes.

2. Remove raise_exceptions=True from server.run() (Fixes #4213)

• Problem: server.run(..., raise_exceptions=True) crashed the server process on malformed JSON-RPC messages instead of returning a JSON-RPC error response (following the fix applied to fetch server in fix(fetch): handle malformed input without crashing #3515).
• Fix: Removed raise_exceptions=True from server.run().

Verification

• Added 4 new regression tests in src/git/tests/test_server.py.
• pytest executed: 47 passed in 2.65s.
• ruff check and pyright both passed with 0 errors.

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cc @olaservo for review when available. Thank you!