chore: rebrand companion-os to clanker-agent

- Rename all package names from companion-* to clanker-*
- Update npm scopes from @mariozechner to @harivansh-afk
- Rename config directories .companion -> .clanker
- Rename environment variables COMPANION_* -> CLANKER_*
- Update all documentation, README files, and install scripts
- Rename package directories (companion-channels, companion-grind, companion-teams)
- Update GitHub URLs to harivansh-afk/clanker-agent
- Preserve full git history from companion-cloud monorepo

packages/coding-agent/clanker-out/docs/prompt-templates.md

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+> clanker can create prompt templates. Ask it to build one for your workflow.
+
+# Prompt Templates
+
+Prompt templates are Markdown snippets that expand into full prompts. Type `/name` in the editor to invoke a template, where `name` is the filename without `.md`.
+
+## Locations
+
+Clanker loads prompt templates from:
+
+- Global: `~/.clanker/agent/prompts/*.md`
+- Project: `.clanker/prompts/*.md`
+- Packages: `prompts/` directories or `clanker.prompts` entries in `package.json`
+- Settings: `prompts` array with files or directories
+- CLI: `--prompt-template <path>` (repeatable)
+
+Disable discovery with `--no-prompt-templates`.
+
+## Format
+
+```markdown
+---
+description: Review staged git changes
+---
+
+Review the staged changes (`git diff --cached`). Focus on:
+
+- Bugs and logic errors
+- Security issues
+- Error handling gaps
+```
+
+- The filename becomes the command name. `review.md` becomes `/review`.
+- `description` is optional. If missing, the first non-empty line is used.
+
+## Usage
+
+Type `/` followed by the template name in the editor. Autocomplete shows available templates with descriptions.
+
+```
+/review                           # Expands review.md
+/component Button                 # Expands with argument
+/component Button "click handler" # Multiple arguments
+```
+
+## Arguments
+
+Templates support positional arguments and simple slicing:
+
+- `$1`, `$2`, ... positional args
+- `$@` or `$ARGUMENTS` for all args joined
+- `${@:N}` for args from the Nth position (1-indexed)
+- `${@:N:L}` for `L` args starting at N
+
+Example:
+
+```markdown
+---
+description: Create a component
+---
+
+Create a React component named $1 with features: $@
+```
+
+Usage: `/component Button "onClick handler" "disabled support"`
+
+## Loading Rules
+
+- Template discovery in `prompts/` is non-recursive.
+- If you want templates in subdirectories, add them explicitly via `prompts` settings or a package manifest.