[segran2]

When an EV delivers no power or less than requested, FTW can receive device_reason from the charger and still show “The charger has not said why.” This change displays the fresh charger-reported explanation for zero delivery, reduced power, lower offered current and device current limits, while preserving Core’s status, severity and measured shortfall.

A reported charger reason also takes precedence over the calculated site-headroom fallback. Stale readings and empty or invalid explanations retain the existing fallback. Excess power, wrong direction, known faults and the dedicated load-balancer status retain their existing messages.

Dependency

Stacked on srcfl#1762 (fix/ev-inferred-site-headroom-1761, dbf47b5), which is itself stacked on srcfl#1537. This PR targets the srcfl#1762 branch in this fork so the diff contains only this fix. Preserve that dependency order and retarget/rebase upstream after the parent changes land. Includes a patch changeset. The installable app vendors this module and will need the updated copy.

Validation

• Focused control-feedback tests and the full npm test suite pass (93 test files).
• Regression cases cover paused/reduced charging, lower current offers, device limits, stale/missing/invalid reasons, precedence over inferred headroom, and preservation of other warnings.
• The complete Go test suite passes after syncing the ignored, generated drivers to the dependency chain's pinned commit. Initial attempts exposed sandbox socket restrictions and stale generated drivers; neither required changes to this PR.
• make verify proceeds through Go tests and release/compose checks, but stops in the existing Docker mDNS test because the Debian image cannot install its apt packages. Full verification is therefore not green in this environment.
• A browser-rendered component preview at 390 px covers paused charging, reduced power and lower offered current. This is a component preview, not a full application or real-hardware acceptance test.
• Human inspection of the rendered UI and affected-hardware validation remain pending. No RPi or charging configuration was changed.