feat(canary): synthesised-artifact generators + tests

Five built-in generators that produce deterministic fake artifacts
keyed by the token slug:

- aws_creds  — passive [default]/[prod] credentials block, no
               callback wiring (AWS-key tokens require an external
               trap, which is post-v1)
- git_config — .git/config with origin url = http_base/c/<slug>/repo.git
- env_file   — .env with API_BASE_URL + WEBHOOK_NOTIFY_URL embedding
               the callback URL plus inert realism filler
- ssh_key    — PEM-shaped fake private key whose host comment carries
               <slug>.<dns_zone> when DNS is deployed, else the
               http_base host
- honeydoc   — minimal HTML report with a 1x1 tracking-pixel <img>
               whose src is the callback URL; fallback for the
               deploy-time baseline before the operator uploads a
               real DOCX/PDF

Tests assert byte-stability (same ctx -> same bytes), slug presence
in the embedded fields, that aws_creds is intentionally URL-free,
and that every artifact carries operator-facing notes for the
preview endpoint.

decnet/canary/generators/aws_creds.py

@@ -0,0 +1,86 @@
+"""Fake ``~/.aws/credentials`` block (passive bait).
+
+This is the **passive** variant — no callback wiring.  An attacker
+who exfils these keys can't trip a detection unless we run a real
+AWS account with a deny-all CloudTrail listener (post-v1).  The
+realism is the point: the file looks like a routinely used credentials
+file, so the rest of the decky's persona feels lived-in.
+
+If the operator picks ``kind="aws_passive"`` we accept that no slug
+will be embedded.  If they pick ``kind="http"`` or ``kind="dns"`` for
+this generator, the API will reject the combination with a 400 — AWS
+keys have no plausible field where a URL or hostname survives a
+``grep -E '[A-Z0-9]{20}'`` smell test.
+"""
+from __future__ import annotations
+
+import hashlib
+from secrets import token_urlsafe
+
+from decnet.canary.base import CanaryArtifact, CanaryContext, CanaryGenerator
+
+
+# Stable AWS-style key body derived from the slug.  Keeping the
+# generator deterministic (per-slug) means re-seeding produces the
+# same bytes — the planter is naturally idempotent and an operator
+# who runs ``decnet canary verify`` can re-derive the expected file
+# without touching the DB.
+
+def _fake_access_key(seed: str) -> str:
+    # AWS access keys are 20 chars, uppercase alphanum, AKIA prefix.
+    body = hashlib.sha256(seed.encode()).hexdigest().upper()
+    return "AKIA" + body[:16]
+
+
+def _fake_secret_key(seed: str) -> str:
+    # AWS secret keys are 40 chars, mixed-case base64-ish.  We use
+    # base64-safe characters from token_urlsafe seeded by a SHA-256
+    # of the seed so the output is stable per slug.
+    h = hashlib.sha256(("secret:" + seed).encode()).digest()
+    # Reuse token_urlsafe for the alphabet but pad to 40 chars from
+    # the deterministic bytes so we don't depend on os.urandom.
+    import base64
+    return base64.b64encode(h)[:40].decode()
+
+
+class AWSCredsGenerator(CanaryGenerator):
+    name = "aws_creds"
+
+    def generate(self, ctx: CanaryContext) -> CanaryArtifact:
+        seed = ctx.callback_token
+        access = _fake_access_key(seed)
+        secret = _fake_secret_key(seed)
+        body = (
+            "[default]\n"
+            f"aws_access_key_id = {access}\n"
+            f"aws_secret_access_key = {secret}\n"
+            "region = us-east-1\n"
+            "\n"
+            "[prod]\n"
+            f"aws_access_key_id = {_fake_access_key('prod-' + seed)}\n"
+            f"aws_secret_access_key = {_fake_secret_key('prod-' + seed)}\n"
+            "region = us-west-2\n"
+        )
+        return CanaryArtifact(
+            path="",  # caller (planter) fills this from CanaryToken.placement_path
+            content=body.encode("utf-8"),
+            mode=0o600,
+            mtime_offset=-86400 * 14,  # 2 weeks ago — looks lived-in
+            generator=self.name,
+            notes=[
+                "fake AWS keys; no callback embedded — passive bait only",
+                f"derived deterministically from slug={seed}",
+            ],
+        )
+
+
+# Re-exported so the slug helper is reusable from the
+# instrumenters/passthrough module without an internal import path.
+__all__ = ["AWSCredsGenerator", "_fake_access_key", "_fake_secret_key"]
+
+
+# Imports at the bottom keep the public dataclasses on top — pylint
+# doesn't run on this repo, but tests do, and putting ``token_urlsafe``
+# in a public symbol confuses readers.  Suppress the unused warning by
+# referencing it once.
+_ = token_urlsafe