fix: clarify installed workflow_dir is an absolute path (#3469)

The documentation for context.workflow_dir described the installed-by-ID
case as ".specify/workflows/<id>/" which appears relative, contradicting
the "resolved absolute path" semantics. Clarified that it is the absolute
path to the installation directory.

Assisted-By: 🤖 Claude Code

Author: rhuss

workflows/README.md

@@ -348,7 +348,7 @@ current run:
 | Variable | Description |
 |----------|-------------|
 | `context.run_id` | The current workflow run id (the same value Spec Kit prints as `Run ID:` at the end of `workflow run`). Auto-generated runs are 8-character hex from `uuid4`; operator-supplied ids may be any alphanumeric string with hyphens or underscores. Empty string outside a run context. |
-| `context.workflow_dir` | The resolved absolute path to the directory containing the workflow source file. For file-loaded workflows this is the parent directory of the YAML file; for installed-by-ID workflows it is `.specify/workflows/<id>/`; for string-loaded workflows it is an empty string. On resume the original source directory is preserved from the first execution. |
+| `context.workflow_dir` | The resolved absolute path to the directory containing the workflow source file. For file-loaded workflows this is the parent directory of the YAML file; for installed-by-ID workflows it is the absolute path to the installation directory (e.g. `<project>/.specify/workflows/<id>/`); for string-loaded workflows it is an empty string. On resume the original source directory is preserved from the first execution. |
 
 ```yaml
 # Stamp telemetry events with the run id for cross-system join.