fix: resolve the issue store path independently of the working directory

ISSUE_ROOT was the relative `tmp/issues`, so "the store" was whatever
directory the shell happened to be standing in. It is the --out default
in all eight scripts of both layers, which made one `cd` — and a `cd`
outlives the command that ran it — enough for readers to report an empty
store on a full one and for writers to quietly build a second store
beside the first. `issue_index.py` run from inside tmp/issues left
tmp/issues/tmp/issues/ behind and exited 0.

The anchor is issue.py's own __file__, not cwd. A script's location is a
fact about the installation; cwd is a fact about the last `cd`, and the
scripts are invoked by path from wherever the agent happens to be. From
there `store_root()` walks up to the nearest repo marker — `.git`
(exists(), not isdir(): a worktree's .git is a file) or AGENTS.md for a
copy taken out of git — and joins tmp/issues. Markers rather than a
fixed number of `..` hops, because the layout is not a promise. cwd is
tried only if the scripts are not inside a repository at all.

The function lives in the domain layer and skills/sync imports it, so
both layers agree by construction — the direction the layering rule
allows. skills/issue stays stdlib-only.

An explicit --out still wins and is used exactly as typed: a relative
--out stays relative to cwd, because that is what the operator asked
for. No new environment surface.

Two consequences the issue also asked for:

- Missing is no longer reported as empty. `store_error()` returns one
  message for a path that is not there and another for a store with no
  issues in it.
- Nothing conjures a store as a side effect of a write. save() and
  issue_index.build() require it instead of os.makedirs'ing it; only
  issue_new.py and pull.py create one, and both say so on stderr.

Establishes tests/ — plain stdlib unittest, no pytest, no dependencies.
The store tests build a throwaway repo in a TemporaryDirectory (a .git
marker, a copy of both script layers, fixture issues) and run the real
scripts inside it as subprocesses from five different working
directories; tmp/issues/ is never touched. Against the pre-fix scripts
15 of the 21 fail, reproducing the report exactly — five stray stores,
including tmp/issues/tmp/issues.

    python3 -m unittest discover -s tests -v

Closes claude-skills/tea#15

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

skills/issue/scripts/issue.py

@@ -48,7 +48,67 @@ without a parser:
 import os
 import re
 
-ISSUE_ROOT = os.path.join("tmp", "issues")
+# --------------------------------------------------------------------------
+# where the store lives
+# --------------------------------------------------------------------------
+# `<repo root>/tmp/issues`, absolute, resolved once at import.
+#
+# It used to be the relative `tmp/issues`, which made "the store" whatever
+# directory the shell happened to be standing in. One `cd` — and a `cd` outlives
+# the command that ran it — was enough for readers to report an empty store on a
+# full one and for writers to quietly build a second store beside the first.
+#
+# The anchor is THIS FILE, not the working directory. A script's own location is
+# a fact about the installation; cwd is a fact about the last `cd`. Walking up
+# from __file__ therefore hands every script in both layers the same answer no
+# matter where it is invoked from — including from inside tmp/issues itself.
+#
+# An explicit --out still wins over all of this, and is used exactly as typed: a
+# relative --out stays relative to cwd, because that is what the operator asked
+# for. There is no environment override; the store is where the repo is.
+
+STORE_PARTS = ("tmp", "issues")
+
+# `.git` is a directory in a normal clone and a FILE in a worktree — hence
+# exists(), not isdir(). AGENTS.md is the fallback for a plugin copied out of
+# git; the agents-sync hook only ever puts one at a repository root.
+REPO_MARKERS = (".git", "AGENTS.md")
+
+_HERE = os.path.dirname(os.path.abspath(__file__))
+
+
+def repo_root(start):
+    """Nearest ancestor of `start` (inclusive) carrying a repo marker, or None.
+
+    Markers, not a fixed number of `..` hops: how deep this file sits below the
+    root is an implementation detail of the repo layout, and the layout is not
+    a promise."""
+    d = os.path.abspath(start)
+    while True:
+        if any(os.path.exists(os.path.join(d, m)) for m in REPO_MARKERS):
+            return d
+        parent = os.path.dirname(d)
+        if parent == d:
+            return None
+        d = parent
+
+
+def store_root(start=None):
+    """Absolute path of the issue store.
+
+    `start` overrides the anchor and exists so the resolution can be exercised
+    against a scratch tree. When these scripts are not inside a repository at
+    all, cwd gets a turn; failing that the historical cwd-relative location
+    stands, made absolute so an error message can name the directory it really
+    looked in."""
+    for anchor in ([start] if start is not None else [_HERE, os.getcwd()]):
+        root = repo_root(anchor)
+        if root:
+            return os.path.join(root, *STORE_PARTS)
+    return os.path.abspath(os.path.join(*STORE_PARTS))
+
+
+ISSUE_ROOT = store_root()
 
 # Domain-owned metadata, in render order. Foreign keys render after these,
 # sorted, so the sync layer can add fields without touching this list.
@@ -356,6 +416,55 @@ def validate(issue, known_ids=None):
 # store
 # --------------------------------------------------------------------------
 
+class StoreMissing(Exception):
+    """The store directory is not there.
+
+    Deliberately a different answer from "the store is empty". One is a path
+    that does not exist, the other is a repository with no issues filed yet, and
+    conflating the two is exactly what made a missed directory look like an
+    empty backlog."""
+
+    def __init__(self, root):
+        self.root = root
+        Exception.__init__(self, "store %s does not exist" % root)
+
+
+def store_exists(root):
+    return os.path.isdir(root)
+
+
+def require_store(root):
+    """Assert the store is there before reading or writing it."""
+    if not os.path.isdir(root):
+        raise StoreMissing(root)
+    return root
+
+
+def create_store(root):
+    """Create the store; True when it actually made the directory.
+
+    Only the commands that legitimately bootstrap a store call this — issue_new
+    and pull — and both announce it. Nothing creates a store as a side effect of
+    a write any more: a missing directory is something to report, not something
+    to conjure."""
+    if os.path.isdir(root):
+        return False
+    os.makedirs(root)
+    return True
+
+
+def store_error(root):
+    """Why `root` cannot be read as a store, or None when it holds issues.
+
+    The two messages are distinct on purpose — see StoreMissing."""
+    if not os.path.isdir(root):
+        return ("store %s does not exist — nothing was created; pass --out to "
+                "point elsewhere" % root)
+    if not all_ids(root):
+        return "store %s exists but is empty" % root
+    return None
+
+
 def path_of(root, id):
     return os.path.join(root, "%s.md" % id)
 
@@ -377,7 +486,7 @@ def load_all(root):
 
 
 def save(root, issue):
-    os.makedirs(root, exist_ok=True)
+    require_store(root)
     p = path_of(root, issue.id)
     with open(p, "w") as f:
         f.write(issue.to_text())