I've drawn all eight concept marks and the comparison sheet. All eight pass the construction checks, but concept 5 doesn't really read as "imd".

Concepts:

1. Lower-case i: the dot is a short upright bar standing above the letter, like the C's bar turned vertical.
2. Capital I: the stem pushes up through the top bar.
3. U: the C turned so it opens upward, with its bar rising out of the top.
4. D: one stroke. The stem overshoots the top, and the right side steps in at both corners so it doesn't read as O or 0.
5. imd monogram in one continuous stroke: see the shortfalls below.
6. Agents converging: five parallel strokes run into one upright, and a single longer bar leaves out the far side.
7. Agreement in a U: inside a U, two short strokes join into one, which rises out of the open top.
8. Converging spiral: one stroke winds inward to a point, and its top bar pushes past the right edge.

Output:

• artifacts/concept-1.png to concept-8.png: 1024 × 1024 PNG. Each image contains only the two colours #16202E and #F7F5EF, with no anti-aliasing. Strokes are 64 px wide (32 px per grid unit), and each mark is centred.
• artifacts/sheet.png: 1856 × 400 PNG, concepts 1 to 8 left to right, with no labels. Each column shows the mark large, then at true 32 px, then the dark-mode version (#eeeeee on #111111) at true 32 px.

Checks: a script checks that every corner point is on the grid, there are no diagonal lines, and no parallel strokes sit close enough to merge into a thicker band. I also looked at the sheet and at concepts 5, 7 and 8 at full size. None needed redrawing.

Where they fall short:

• Concept 5: one stroke can't draw an m's middle stem without a branch. So the m is a single arch and the i has no dot, and the mark reads more like a Greek-key pattern than the letters.
• Concept 2 can look like a cross or dagger (†).
• Concepts 6, 7 and 8 are dense. At 16 px their gaps shrink to 1 px.
• 16 px: I didn't render anything at 16 px, so how they read at that size is untested.
• Multiple strokes: concepts 1, 2, 3, 6 and 7 use more than one stroke, as the current favicon does (the C plus its bar). Only 4, 5 and 8 are a single stroke.

The README with one entry per concept and these shortfalls is docs/marks/README.md, and the main README.md now links to it. Running python3 tools/marks.py regenerates everything and reruns the checks; it needs only standard Python. There are also SVG versions in docs/marks/ that switch to dark mode the way the favicon does.

I committed the script, the SVGs and the README changes on a new branch, marks-concepts. The PNGs in artifacts/ are left uncommitted for upload, as instructed.