fix(discover+ccusage): Windows drive colon not sanitized in slug + accept ccusage 20.x 'period' field

[mickel-am]

Two independent bugs found running rtk on Windows (Win10) with ccusage 20.9.

Bug 1 — rtk discover scans 0 sessions on Windows

Affected: all Windows paths with a drive letter (e.g. f:\AMPLIA_APP 1)

Root cause: encode_project_path in src/discover/provider.rs did not include : in SANITIZED_CHARS. Claude Code replaces both backslash and colon with - when generating project slugs:

f:\AMPLIA_APP 1  →  f--AMPLIA-APP-1   (Claude Code / actual directory)
f:\AMPLIA_APP 1  →  f:-AMPLIA-APP-1   (RTK before this fix)

The substring match in discover_sessions_in_projects_dir always missed every project directory on Windows.

Fix: Add : to SANITIZED_CHARS.

• Corrects the test_encode_project_path_windows assertion (was asserting the wrong slug)
• Adds test_encode_project_path_windows_with_space as a regression test

Bug 2 — rtk cc-economics shows $0 with ccusage ≥ 20.x

Root cause: ccusage 20.x changed the monthly JSON field from "month" to "period" in the all-agents response. Serde deserialization silently returned Ok(None), zeroing out the economics report.

Fix: Add #[serde(alias = "period")] to MonthlyEntry.month in src/analytics/ccusage.rs — backwards-compatible, accepts both old and new field names.

• Adds test_parse_monthly_period_field as a regression test

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[rtk-release-bot]

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[KuSh]

Thanks for chasing both of these down on a real Windows box. The drive-letter colon in the project slug was fixed by #2952, merged on 2026-08-13, which added ':' to SANITIZED_CHARS in src/discover/provider.rs and corrected the Windows test to expect C--Users-foo-bar. The ccusage field rename was fixed by #2732, merged on 2026-07-07, which added the "period" serde alias to the daily, weekly and monthly entries with a test for each, so the monthly alias here is already present. The only thing left is the combined f:\AMPLIA_APP 1 test input, and both halves of what it asserts are covered by the existing colon and space tests. Closing as covered, but please comment or reopen if you think a case was missed.