fix: bug: TOML [agents.X] section name with dash crashes load-project.sh (#862)

TOML allows dashes in bare keys, so `[agents.dev-qwen2]` is a valid
section. Before this fix, load-project.sh derived bash var names via
Python `.upper()` alone, which kept the dash and produced
`AGENT_DEV-QWEN2_BASE_URL` — an invalid shell identifier. Under
`set -euo pipefail` the subsequent `export` aborted the whole file,
silently taking the factory down on the N+1 run after a dashed agent
was hired via `disinto hire-an-agent`.

Normalize via `.upper().replace('-', '_')` to match the
`tr 'a-z-' 'A-Z_'` convention already used by hire-agent.sh (#834)
and generators.sh (#852). Also harden hire-agent.sh to reject invalid
agent names at hire time (before any Forgejo side effects), so
unparseable TOML sections never land on disk.

- `lib/load-project.sh` — dash-to-underscore in emitted shell var names
- `lib/hire-agent.sh` — validate agent name against
  `^[a-z]([a-z0-9]|-[a-z0-9])*$` up front
- `tests/lib-load-project.bats` — regression guard covering the parse
  path and the hire-time reject path

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/hire-agent.sh

@@ -30,6 +30,29 @@ disinto_hire_an_agent() {
     echo "Usage: disinto hire-an-agent <agent-name> <role> [--formula <path>] [--local-model <url>] [--model <name>] [--poll-interval <seconds>]" >&2
     exit 1
   fi
+
+  # Validate agent name before any side effects (Forgejo user creation, TOML
+  # write, token issuance). The name flows through several systems that have
+  # stricter rules than the raw TOML spec:
+  #   - load-project.sh emits shell vars keyed by the name (dashes are mapped
+  #     to underscores via tr 'a-z-' 'A-Z_')
+  #   - generators.sh emits a docker-compose service name `agents-<name>` and
+  #     uppercases it for env var keys (#852 tracks the `^^` bug; we keep the
+  #     grammar tight here so that fix can happen without re-validation)
+  #   - Forgejo usernames are lowercase alnum + dash
+  # Constraint: start with a lowercase letter, contain only [a-z0-9-], end
+  # with a lowercase letter or digit (no trailing dash), no consecutive
+  # dashes. Rejecting at hire-time prevents unparseable TOML sections like
+  # [agents.dev-qwen2] from landing on disk and crashing load-project.sh on
+  # the next `disinto up` (#862).
+  if ! [[ "$agent_name" =~ ^[a-z]([a-z0-9]|-[a-z0-9])*$ ]]; then
+    echo "Error: invalid agent name '${agent_name}'" >&2
+    echo "  Agent names must match: ^[a-z]([a-z0-9]|-[a-z0-9])*$" >&2
+    echo "  (lowercase letters/digits/single dashes, starts with letter, ends with alphanumeric)" >&2
+    echo "  Examples: dev, dev-qwen2, review-qwen, planner" >&2
+    exit 1
+  fi
+
   shift 2
 
   # Parse flags