feat(python): classify executable source surfaces

[chrisknvidia]

Summary

• classify Python execution surfaces from raw bytes across .py, .pyw, PEP 263 encodings, extensionless shebangs, and ambiguous inputs
• model platform-specific /usr/bin/env behavior for CPython, PyPy, and uv script launchers, failing closed when execution depends on platform, aliases, options, or invocation spelling
• propagate classification through artifact inventory, nested/transitive analysis, static and behavioral analyzers, build context, inspection ledgers, and provider-cache boundaries
• preserve exact decoded Python for analysis while keeping bounded provider views and preventing local-only, hidden, or nested content leakage

Review context

This is the Python decoding, shebang/platform-command parsing, and execution-surface split requested in the review of #497.

Stacked dependency: #578, which itself depends on #576 and #577. Until those land and this branch is rebased, GitHub's combined diff includes the dependency stack. The Python-only review range is:

git diff d856d88c289c5ef3389060ef69651c9981aae38f..266d42e050493dad869fe50be420ace97914ea82

That delta is 23 files (+5,211/-89). This PR remains draft until its dependencies land, it is rebased onto current main, hosted CI passes at the rebased head, and a current-head human review is complete.

Validation

• regression-first classifier, cache, provider-boundary, ledger, analyzer-routing, and uv launcher coverage
• integrated focused matrix: 1,339 passed, 1 skipped
• independent overlap audits: clean; all 11 replayed patches range-diff identical and final A2 cap/identity behavior preserved
• full configured suite: 6,060 passed, 14 skipped, 39 deselected, 4 expected xfails
• Ruff and formatting clean; all 11 changed source files free of new mypy errors
• wheel built and installed into a fresh environment
• installed CLI JSON, Markdown, and SARIF scans produced the expected TM1 findings and partial-completeness reasons for ambiguous/decode-error inputs
• real uv runtime covered -s, --script, --gui-script, macOS case aliases, global options, and option-like paths
• installed provider-boundary probe preserved exact bounded Latin-1 content while excluding local-only, hidden, and nested source

No live LLM/provider call was run; the configured 39 provider/live integration tests remain deselected.

[rng1995]

Reviewed exact draft head 266d42e050493dad869fe50be420ace97914ea82. I found no additional blocker in the focused Python execution-surface range (d856d88..266d42e): 1,118 affected tests passed with 1 skip, 732 current-main merged-tree regressions passed, and lint/format/diff checks are clean.

I am requesting changes because the current combined tree still contains the confirmed #576/#577 blockers: a three-row ledger cap drops a second distinct fatal fact, and a definitely true bound shell= value evades TM1 when a later argument is effectful. This PR also inherits draft #578 and explicitly requires the dependency stack to land, rebase onto current main, fresh exact-head CI, and current-head review.

Please propagate the dependency fixes and rebase. If the focused range remains semantically unchanged and CI stays green, I found it otherwise suitable for approval.