docs(agent): update supported agents list and clarify agent install behavior

- Revise CONTRIBUTING.md to describe universal vs symlinked agent targets and requirements for adding new targets
- Update DOCUMENTATION.md to clarify agent install command usage and differentiate universal and symlinked agents
- Expand README.md with a detailed supported agents table, including canonical ids, aliases, and skills folder locations
- Update src/lib/agent-targets.ts with added agents, corrections to skillsDir and universal flags, and alias mappings
- Modify unit tests and e2e tests to reflect renamed and updated agent targets, replacing deprecated aliases like gemini-cli with antigravity-cli and windsurf with devin-desktop
- Ensure single source of truth for skills at `.agents/skills`, symlink strategy for non-universal agents, and consistency across docs and code

Author: powxenv

CONTRIBUTING.md

@@ -56,12 +56,21 @@ Pre-decided policies, so proposals don't have to relitigate them:
   runtime dependency needs explicit maintainer sign-off **in the issue,
   before the PR**. Utility modules land only together with the consumer
   that uses them — standalone libraries are declined.
-- **`agent install` targets.** Shipped: `claude`, `antigravity`, `cursor`,
-  `cline`, `codex`, `kiro`, `windsurf`, `copilot`. Accepted and in progress:
-  `gemini`.
-  A proposal for a new target needs (1) the editor's official rules/skill
-  file mechanism, documented, and (2) the proposer prepared to maintain the
-  target going forward.
+- **`agent install` targets.** The CLI supports a registry of agent ids (see
+  the [supported-agents tables](./README.md#supported-agents) in the README for
+  the current set), each classified as **universal** (reads the shared
+  `.agents/skills/` folder directly — Cursor, Codex, Copilot, Amp, …; one
+  install serves all of them) or **symlinked** (keeps skills in its own folder,
+  e.g. `.claude/skills`, with a per-skill symlink back to `.agents/skills/` so
+  every agent reads the same single source of truth). A proposal adding a
+  target must, in the same PR: (1) cite the agent's **current** skills docs
+  proving its skills folder and classification (universal = reads
+  `.agents/skills/` natively; symlinked = installs into its own `<dir>`); (2)
+  add it to the registry (`src/lib/agent-targets.ts` — id, `skillsDir`,
+  `universal` flag, and any alias); (3) update the unit-test target list
+  (`src/lib/agent-targets.test.ts`); and (4) add a row to the matching
+  supported-agents table in the README, with the agent's name and a link to its
+  skills docs.
 - **Outbound network calls.** The CLI talks only to the configured
   TestSprite API endpoint. The one approved exception is an opt-out-able
   npm registry version check (at most once per 24h, carrying nothing but

DOCUMENTATION.md

@@ -109,20 +109,22 @@ Every artifact in the bundle shares one `snapshotId`; the CLI will not mix a fai
 `testsprite agent install` writes the TestSprite skills into your project so your coding agent knows the commands, the exit codes, and the failure-bundle layout — no prompt engineering required. It's a pure-local command: no network, no credentials.
 
 ```bash
-testsprite agent install claude-code    # .agents/skills/<skill>/SKILL.md + .claude/skills/<skill> symlink
-testsprite agent install codex          # writes the canonical copy (Codex reads .agents/skills directly)
-testsprite agent install cursor         # universal — reads the canonical copy
-testsprite agent install gemini-cli     # universal
-testsprite agent install github-copilot # universal
-testsprite agent install kiro-cli       # .kiro/skills/<skill> symlink → canonical
-testsprite agent install windsurf       # .windsurf/skills/<skill> symlink → canonical
-testsprite agent list                   # every supported agent, its skills folder, and universal vs symlink
-testsprite agent status                 # check installed skills against this CLI version
+testsprite agent install claude-code
+testsprite agent install codex
+testsprite agent install cursor
+testsprite agent install kiro-cli
+testsprite agent list
+testsprite agent status
 ```
 
-`--target` accepts any agent id from the standard registry (70+), plus the legacy short aliases (`claude`, `codex`, `cursor`, `cline`, `antigravity`, `kiro`, `windsurf`, `copilot`). Omitting `--target` in a non-interactive shell defaults to `claude-code`; in a terminal the CLI prompts.
+`--target` accepts any agent id from the registry — see [Supported agents](./README.md#supported-agents) in the README for the full list. Omitting `--target` in a non-interactive shell defaults to `claude-code`; in a terminal the CLI prompts.
 
-Because every universal agent reads the same `.agents/skills/` folder, **installing for one universal agent makes the skill available to all of them** — `agent install --target codex` also serves Cursor, Cline, Gemini CLI, Copilot, etc.
+There are two kinds of agent:
+
+- **Universal agents** (Skills folder `.agents/skills`) read the skill directly from the shared folder. Installing for **one** of them makes the skill available to **all** of them — `agent install --target codex` also serves Cursor, Copilot, Amp, and every other universal agent.
+- **Symlinked agents** (every other folder) get a per-skill symlink from their own skills folder back to `.agents/skills/`, so they read the same bytes as the universal ones.
+
+`.agents/skills/` is the **single source of truth**: it is written on every install, even when you target a symlinked agent — `agent install --target claude-code` lands the skill in `.agents/skills/` (covering every universal agent) **and** links it into `.claude/skills/`. Because each symlink points _into_ `.agents/skills/`, you only ever edit a skill there and every symlinked agent reflects the change automatically (on systems where symlinks are unavailable — e.g. Windows without Developer Mode — a plain copy is written instead, which won't auto-update).
 
 `agent status` checks the canonical skill file (and each symlinked landing) against the current CLI version and reports `ok`, `stale`, `modified`, or `unmarked` for every agent that has an install (absent agents are omitted to keep output focused). It exits `1` when anything needs attention, so `testsprite agent status && …` can gate a CI step; `--dir <path>` inspects a different project root.