Add search subcommand with tag, date, and project filters

[Intina47]

Motivation

• Provide a way to slice and find notebook entries by tag, date range, and project/repo context from the CLI.
• Support combinable filters so users can run searches like jot search "incident" --tag prod --since 2024-01-01 --project myrepo.

Description

• Add a search subcommand and flag parsing in main.go with repeatable --tag, --since, --until, and --project flags and a runJotSearch entrypoint.
• Implement entry parsing (parseEntry) plus helpers for date-only comparison (dateOnly, parseDateInput), tag/project extraction (tagRegex, projectRegex, entryHasTags, entryHasProject), and normalization (normalizeSlice).
• Implement the main search engine jotSearch which applies text query, tag, project, and date-range filters combinatorially and streams matched lines to the writer.
• Document the new jot search usage and conventions in README.md and add unit tests covering tag, date-range, and project filtering in main_test.go.

Testing

• Ran go test ./... and the test suite passed (all tests succeeded).
• Added unit tests TestJotSearchFiltersByTag, TestJotSearchFiltersByDate, and TestJotSearchFiltersByProject which exercise the new filtering logic and passed during the test run.

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Parse flags before query or filters are ignored

Go’s flag.FlagSet.Parse stops at the first non-flag argument, so with the documented usage jot search "incident" --tag prod the parser will stop at incident and leave --tag prod in flags.Args(). That means opts.tags/since/until/project stay empty and the query becomes incident --tag prod, silently disabling filtering. This makes the new filters unusable unless users put all flags before the query (or use --). Consider supporting interspersed flags (e.g., custom parsing or pflag) or enforcing/communicating a flags-before-query convention.

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