fix(cli): reject invalid time filters

[samzong]

Summary

• reject unsupported explicit time filters across search, session list, usage, and export
• preserve the default all range, documented aliases, case-insensitive parsing, and raw JSON filter values
• make the shared time parser fail closed for non-CLI callers

Verification

• cargo test cli::tests::time_filter_validates_values_for_every_command -- --exact
• black-box probes: all four commands exit 2 for --time definitely-invalid
• make check

[samzong]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Already looking forward to the next diff.

Reviewed commit: 421885219c

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