* build: stage product_qa docs corpus from mksite (no vendoring)

The mcp-side plumbing that pairs with the merged backend workflow
(deploy-public-demo-mcp staging mksite docs). The image now COPYs
config/mksite/docs and stages it into build/product-kb/docs, where the
product-kb loader reads the corpus. Docs are NOT vendored — the repo keeps only
config/mksite/docs/.gitkeep so the COPY can't fail; CI fills it from mksite, and
local `npm run build` sources the sibling ../mksite/docs (override via
LOG10X_PRODUCT_KB_SRC, non-fatal when absent).

NOTE: inert on main until the log10x_product_qa tool/loader lands (currently on
fix/composite-arc-rerun) — until then the staged docs are shipped but unread.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* chore: bump version to 1.12.2 (satisfies version-bump-check)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Dor Levi <11015255+dor-levi@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>