Preserve scoped Phase-A audit receipts

[RMANOV]

What

Closes all four actionable post-merge findings from #8:

• preserve one sweep receipt per date, real/synthetic scope, and hashed campaign ID
• fail closed when analyze() receives an explicit campaign absent from the selected scope
• remove the midnight boundary flake from the foreign-campaign regression
• cache Unicode character counts in the opt-in language-correction path

Verification

• targeted new regressions: 4 PASS
• full Python suite: 84 PASS, 1 skip
• focused Rust autocorrect tests: 2 PASS
• Ruff, py_compile, cargo fmt check, diff check: PASS

Commit: b1ac68b

[Copilot]

Pull request overview

This PR closes the remaining post-merge Phase‑A audit findings by ensuring sweep receipts are preserved per campaign/scope/day, analysis fails closed for explicitly unknown campaigns, a midnight-boundary regression test is stabilized, and the Rust language-correction path avoids repeated Unicode character counting.

Changes:

• Write sweep receipts to per-(date, real/synthetic scope, hashed campaign) filenames instead of overwriting a single daily receipt.
• Fail closed in analyze() when an explicit campaign_run_id is not found in the selected scope, matching watchdog behavior.
• Remove test flakiness around midnight boundaries and add a regression asserting multiple campaign receipts are preserved; cache character counts in Rust language correction.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
tests/test_o1_phasea.py	Stabilizes the foreign-campaign regression timing, adds receipt-preservation coverage, and adds an analyze() unknown-campaign failure test.
phase_a/sweep.py	Persists sweep receipts using scope + hashed campaign ID to prevent overwriting across campaigns/scopes.
phase_a/analyze.py	Adds a fail-closed guard when an explicit campaign is missing from the chosen scope.
crates/smartkey-core/src/input.rs	Caches Unicode character counts in the opt-in language correction path to avoid repeated .chars().count() work.

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