Implement non-Rust brand identity surfaces

[donbeave]

Summary

This PR ships the non-Rust slice of the brand identity system: operators and contributors now see the jackin❯ wordmark, j❯ prompt sigil, canonical chevron green, refreshed README/social/icon assets, and brand usage rules across docs, README, repo guidance, web chrome, landing surfaces, generated assets, and the role-container Starship prompt. The canonical long-term spec now lives in the Brand Identity reference page, while the Brand Identity System roadmap records the implemented directions and the Rust CLI/Capsule work intentionally left for the next phase.

Hard rule: brand spelling

This PR flips the agent spelling contract from the apostrophe-era name to jackin❯ in rich-text prose, with jackin> / j> reserved for proven plaintext fallback surfaces and bare jackin reserved for literal commands, packages, paths, config keys, URLs, and code identifiers. The full usage rules live in AGENTS.md and the Brand Identity reference page.

What's deferred (follow-up PRs)

• Rust CLI/Capsule output prefixes, frozen --help banner, version/splash treatment, and Rust snapshot coverage.
• Any deeper app/desktop/mobile implementation beyond the committed source icon assets.
• Host-side prompt installation, which remains out of scope and would require explicit operator opt-in.

Verify locally

Checkout

Paste this first to bypass the tirith paste scanner for the rest of the session:

export TIRITH=0

Then paste the checkout block:

mkdir -p "$HOME/Projects/jackin-project/test/pr-496"
cd "$HOME/Projects/jackin-project/test/pr-496"

if [ ! -d jackin/.git ]; then
  git clone https://github.com/jackin-project/jackin.git
fi

cd jackin
mise trust
git fetch -f origin feature/brand-identity-system:refs/remotes/origin/feature/brand-identity-system
git checkout -B feature/brand-identity-system refs/remotes/origin/feature/brand-identity-system
mise trust
mise install
cargo build --bin jackin
export PATH="$PWD/target/debug:$PATH"
which jackin

Isolation

export JACKIN_CONFIG_DIR="$HOME/.config/jackin-pr-496"
export JACKIN_HOME_DIR="$HOME/.jackin-pr-496"
just construct-build-local
export JACKIN_CONSTRUCT_IMAGE="jackin-local/construct:trixie"

Docs checks

(
  cd docs
  bun install --frozen-lockfile
  bun run build
  bun run check:repo-links
  bunx tsc --noEmit
  bun test
)

User smoke

jackin console --debug

In the console, start an ephemeral shell for the current directory or a saved workspace. The shell should render the Starship prompt as j❯, with the j in the terminal foreground and the chevron in green. The console and launch surfaces should still stay operational first: no logo splash replaces the launch UI, and normal workspace/role/agent selection remains reachable.

For a direct construct prompt check, run:

jackin load agent-smith . --debug

Inside the container, open or switch to a shell pane if the agent runtime does not already leave you at a shell. Verify the prompt uses j❯, and that echo "$JACKIN_AGENT" still reports the active agent slug when the session sets it.

Documentation

(
  cd docs
  bun install --frozen-lockfile
  bun run dev
)

Vite serves at http://localhost:3000/. Pages to walk:

http://localhost:3000/
UPDATED landing page. Confirm the first viewport uses the jackin❯ / by tailrocks lockup, the header uses the split-color wordmark, the terminal panel prompt uses j❯, and the page does not regress into a marketing splash that hides the product surface.

http://localhost:3000/reference/brand-identity/
NEW page in Behind jackin❯ — Internals, between Configuration and Schema Versions. Confirm it documents the valid text forms, byline rules, color tokens, type stack, prompt target, and generated asset inventory.

http://localhost:3000/reference/roadmap/brand-identity-system/
UPDATED roadmap page. Confirm the status is partially implemented, the chosen directions are documented, and Rust CLI/Capsule branding work is explicitly deferred.

http://localhost:3000/getting-started/why/
UPDATED prose sweep sample. Confirm public docs prose uses jackin❯ while command examples and literal package/path references stay jackin.

http://localhost:3000/developing/construct-image/
UPDATED role-authoring page. Confirm the construct prompt row describes the shared j❯ Starship prompt and the active JACKIN_AGENT prefix.

Migration notes

None for operator config or versioned schemas. Operators who want to verify the container prompt before the next published construct image should use the local construct-image override in the Isolation block.