fix(cli): diag selects a device that exposes the feature under test

[recchia]

Closes #148 (Finding 2). Builds on the verification in #148.

first_online_device() returned the first online paired device regardless of
kind. With a keyboard + mouse paired over Bluetooth-direct (each enumerates as
its own inventory), a mouse-only diag picks the keyboard and fails:

device: MX Keys (direct 046d:b35b)
Error: device does not expose HID++ feature 0x2201

This replaces it with select_device(query, required_features):

• diag dpi / diag smartshift now prefer an online device whose HID++ feature
  table advertises the feature under test (0x2201, and 0x2110/0x2111),
  so a paired keyboard is skipped automatically.
• Adds a --device <name> override (case-insensitive substring match).
• On no match, the error lists the online devices instead of a generic message.

Non-breaking: existing invocations work unchanged; diag features and
diag lighting are untouched. Verified on Ubuntu 26.04 / Wayland — with both
devices online, diag dpi now targets the MX Master 3S without powering off the
keyboard, and --device master selects it explicitly.

[greptile-apps]

Greptile Summary

This PR replaces the single-call first_online_device() helper with online_devices() + select_device(), which probes each device's HID++ feature table so mouse-only diagnostics (dpi, smartshift) automatically skip a paired keyboard that lacks the required feature. A --device <name> substring flag is added to dpi, smartshift, and lighting to allow explicit override.

• select_device in mod.rs handles three selection tiers: explicit name query, feature-table probe, then first-online fallback. Probe failures are now surfaced via tracing::warn rather than silently swallowed.
• lighting.rs gets its own --device inline filter (direct-USB path, no feature probe needed).
• Error messages now list all online devices when selection fails, replacing the generic "no online device" text.

Confidence Score: 5/5

Safe to merge — the new device-selection logic handles all three tiers (explicit query, feature probe, first-online fallback) correctly, probe errors are now logged rather than silently swallowed, and the changes are additive to the CLI surface.

The refactor is well-scoped: online_devices + select_device replace a simple helper cleanly, the feature-probe loop degrades gracefully on transient errors, and the --device flag is wired up consistently across the three affected subcommands. No data is mutated or persisted, so the worst-case outcome of any edge case is a clear error message rather than silent corruption.

No files require special attention.

Important Files Changed

Filename	Overview
crates/openlogi-cli/src/cmd/diag/mod.rs	Core selection logic rewritten: online_devices() enumerates all online paired devices; select_device() implements query → feature-probe → first-online tiers. Feature-probe errors are now logged via tracing::warn. Logic is sound.
crates/openlogi-cli/src/cmd/diag/dpi.rs	Adds --device arg; switches to select_device(args.device.as_deref(), &[0x2201]). Straightforward and correct.
crates/openlogi-cli/src/cmd/diag/smartshift.rs	Adds --device arg; switches to select_device(args.device.as_deref(), &[0x2110, 0x2111]). Correctly probes for both SmartShift feature variants.
crates/openlogi-cli/src/cmd/diag/lighting.rs	Adds --device filter inline (direct-USB path, no feature probe needed). Name filter applied before route construction; error message stays simple when a query doesn't match.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["select_device(query, required_features)"] --> B["online_devices()"]
    B --> C{query set?}
    C -- yes --> D["Find first device whose name contains query (case-insensitive)"]
    D -- found --> E["Return (route, name)"]
    D -- not found --> F["no_match_err: list online devices + suggest --device"]
    C -- no --> G{required_features non-empty?}
    G -- yes --> H["For each device: dump_features(route)"]
    H -- "Ok(entries): any feature matches" --> E
    H -- "Ok(entries): no match" --> I["Try next device"]
    H -- "Err(e)" --> J["tracing::warn! + try next device"]
    I --> K{More devices?}
    J --> K
    K -- yes --> H
    K -- no / G=no --> L["devices.into_iter().next()"]
    L -- Some --> E
    L -- None --> M["no_match_err: no online device found"]

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