Feat/fix fdb reader

[mathleur]

Description

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

[Copilot]

Pull request overview

This PR updates the FDB adapter flow and extends Qube’s JSON “arena” serialization/deserialization with a versioned envelope and more explicit coordinate typing (including introducing datetime coordinates), plus adds example outputs and a helper binary for generating JSON snapshots.

Changes:

• Adjust FDB listing behavior and skip creating empty-value children when building a Qube from an FDB list.
• Change arena JSON format to a versioned envelope and introduce typed coordinate encoding/decoding (ints/strings/floats/datetimes).
• Add datetime coordinate type support and expand float coordinate operations/tests; add example JSON artifacts and a new helper binary.

Reviewed changes

Copilot reviewed 17 out of 19 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
qubed_meteo/src/adapters/fdb.rs	Tweaks FDB list invocation and avoids creating empty-coordinate children for key= entries.
qubed_meteo/examples/read_from_fdb_list.rs	Example output switched from ASCII dump to arena JSON printing.
qubed_meteo/bin/fdb_db_reader.rs	New helper binary to build a Qube from FDB and write arena JSON to disk.
qubed_meteo/Cargo.toml	Removes direct rsfdb dependency entry (but code still uses rsfdb).
qubed_meteo/qube_examples/*.json	Adds several committed arena JSON example snapshots.
qubed/src/serde/json.rs	Arena JSON now wrapped in {version, qube} and coords are type-tagged; deserializer updated accordingly.
qubed/src/coordinates/strings.rs	Adds contains helper for string coordinates.
qubed/src/coordinates/ops.rs	Adds NaiveDateTime append/extend support and FromIterator impl for datetime coordinates.
qubed/src/coordinates/mod.rs	Adds DateTimes coordinate variant and JSON serialization support for datetimes.
qubed/src/coordinates/floats.rs	Implements float extend/append/contains/intersect + adds unit tests and conversions.
qubed/src/coordinates/datetime.rs	New datetime coordinate implementation + parsing/intersection + tests.
qubed/Cargo.toml	Adds chrono dependency for datetime support.
.gitignore	Ignores *.bak files.

Comments suppressed due to low confidence (1)

qubed/src/coordinates/ops.rs:86

• When extending from Coordinates::Mixed, the datetime component isn’t merged (mixed.datetimes is omitted), so datetime coords will be dropped when merging two mixed coordinate sets. Include self_mixed.datetimes.extend(&mixed.datetimes) in this branch.

            Coordinates::Mixed(mixed) => match self {
                Coordinates::Mixed(self_mixed) => {
                    self_mixed.integers.extend(&mixed.integers);
                    self_mixed.floats.extend(&mixed.floats);
                    self_mixed.strings.extend(&mixed.strings);
                }

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[Copilot]

@mathleur I've opened a new pull request, #79, to work on those changes. Once the pull request is ready, I'll request review from you.