Expand one brand anchor color into a full, contrast-checked palette instead of guessing at five more hex codes

Act as a color systems consultant. I have one anchor brand color already decided (not negotiable, do not suggest replacing it) and need it expanded into a working palette for a real product, not a moodboard.

ANCHOR COLOR
#2F6FED, a mid-tone blue used in the logo, already approved by the founders — cannot be changed.

WHERE IT WILL BE USED
A web app dashboard (light mode default, dark mode planned for later), plus marketing site hero sections and email templates.

BRAND FEELING TO PRESERVE
Trustworthy fintech feel — calm and precise, not playful or loud; avoid anything that reads as a consumer social app.

ACCESSIBILITY REQUIREMENT
WCAG 2.1 AA for all text and interactive elements (4.5:1 for normal text, 3:1 for large text and UI components).

Step 1 — Diagnose the anchor color first: state its approximate hue/saturation/lightness character and what that means for how far it can shift before it stops reading as "the brand color" versus becoming a believable tint or shade of it. Do this before proposing anything, since a palette built without first understanding the anchor's own limits tends to either drift too far (loses brand recognition) or stay too close (fails contrast requirements).
Step 2 — Propose a full palette: 2-3 tints/shades of the anchor for primary UI use, one secondary/accent color that is NOT simply the anchor's complement unless you argue for why complementary is right here, a neutral gray scale with a hint of the anchor's hue rather than a pure gray (state the hex), and semantic colors for success/warning/error/info that read as their own category rather than random hues that happen to be red or green.
Step 3 — For every color intended for text-on-background or button-on-background use, state the actual contrast ratio against both a light and dark surface and flag explicitly which combinations fail the stated accessibility requirement, rather than presenting a swatch grid where contrast has to be checked later by someone else.
Step 4 — Name one realistic scenario where this palette would visibly break (e.g., a disabled-state button becoming indistinguishable from its enabled state, or a success/error pair that reads identically to a colorblind user) and propose the specific fix.

Do not present hex codes as a flat list with no reasoning attached — every color must be traceable to a stated purpose and a stated contrast result.

OUTPUT FORMAT
1. Anchor diagnosis (2-3 sentences).
2. Full palette as a table: role, hex, contrast ratio against white and against near-black, pass/fail against the stated requirement.
3. The one realistic failure scenario and its fix.
4. A one-paragraph note on what NOT to do with this palette (e.g. don't use the accent color for large background fills).