chore(#489): drop stale Python 3.8/3.9 classifiers from pyproject.toml

[drewdrewthis]

Summary

• Removes Programming Language :: Python :: 3.8 and Programming Language :: Python :: 3.9 from the classifier block in python/pyproject.toml.
• requires-python = ">=3.10" already declares the minimum; the stale 3.8/3.9 entries caused false-positive PyPI search results.
• No doc files with the stale 68 @unit counts were found in-repo (they were never committed or were already absent).

Acceptance criteria (from #489)

• python/pyproject.toml classifier block drops "Programming Language :: Python :: 3.8" and "3.9" entries.
• Any in-repo doc referencing "68 @Unit" updated — grep found zero hits; no files to change.
• docs/proposals/issue-350-prove-it-report.md is absent from the repo (was only on @drewdrewthis's local checkout per the audit report reference); no change needed.

Test plan

• CI passes (Python classifiers are metadata; no runtime behaviour changed)
• python/pyproject.toml contains no 3.8 or 3.9 classifier lines

🤖 Generated with Claude Code

[github-actions]

Automated low-risk assessment

This PR was evaluated against the repository's Low-Risk Pull Requests procedure.

• Scope: Remove "Programming Language :: Python :: 3.8" and "... :: 3.9" classifier entries from python/pyproject.toml (no other files modified).
• Exclusions confirmed: no changes to auth, security settings, database schema, business-critical logic, or external integrations.
• Classification: low-risk-change under the documented policy.

The change only removes stale PyPI trove classifier lines (Python 3.8 and 3.9) from python/pyproject.toml and does not modify authentication, secrets, database schemas, business‑critical logic, or third‑party integrations. Runtime requirements are unchanged (requires-python remains >=3.10), so this is metadata-only and easy to revert if needed.

An approving review has been submitted by automation. The PR may merge once required CI checks pass.

[github-actions]

Approved by automation: PR qualifies as low-risk-change under the documented policy.

[drewdrewthis]

[grinder] READY for human review

CI: green (zero failing, zero pending)
ACs: met — Python 3.8 and 3.9 classifier entries removed from python/pyproject.toml, aligning advertised versions with requires-python = ">=3.10"; no stale doc files found in repo
Threads: zero unresolved

Verified by:
command gh pr checks 555 → all 13 checks pass (test 3.12: pass 5m52s, python-complete: pass, javascript-complete: pass)
command gh pr view 555 --json reviewDecision → APPROVED by github-actions (low-risk-change policy)