feat(workflows): expose workflow source directory to steps (#3469)

* feat(workflows): expose workflow source directory to steps (#3467)

Propagate WorkflowDefinition.source_path to steps via
{{ context.workflow_dir }} in template expressions and
SPECKIT_WORKFLOW_DIR env var for shell steps. The original
source directory is persisted in state.json so resume
restores the correct value instead of the run-directory copy path.

Closes #3467

Assisted-By: 🤖 Claude Code

* fix: apply bot review suggestions (#2)

Applied fixes from bot review comments:
- Comment #3563319058: prevent stale SPECKIT_WORKFLOW_DIR leak from parent env
- Comment #3563319094: use cross-platform Python one-liner instead of printenv
- Comment #3563319103: add monkeypatch.delenv for deterministic env var test
- Comment #3563319116: same env leak fix as #3563319058

Assisted-By: 🤖 Claude Code

* fix: use YAML single-quotes and forward-slash paths for Windows CI (#2)

sys.executable on Windows returns backslash paths (D:\a\...) which YAML
double-quoted strings interpret as escape sequences. Switch to
single-quoted YAML strings and normalize paths with replace("\\", "/").

Assisted-By: 🤖 Claude Code

* fix: resolve workflow_dir to absolute path and add installed-by-ID test (#3469)

Applied fixes from bot review comments:
- Comment #3563382853: resolve source_path before taking parent to ensure absolute paths
- Comment #3563382864: add test for installed-by-ID workflow_dir semantics

Assisted-By: 🤖 Claude Code

* docs: document context.workflow_dir and SPECKIT_WORKFLOW_DIR

Add reference documentation for the new workflow_dir runtime value in
both workflows/README.md and docs/reference/workflows.md so workflow
authors can discover the feature and its semantics.

Assisted-By: 🤖 Claude Code

* 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

* fix: apply bot review suggestions (#3469)

Applied fixes from bot review comments:
- Comment #3580005128: Quote sys.executable in shell step env var test
- Comment #3580005174: Quote sys.executable in no-env-var test

Assisted-By: 🤖 Claude Code

* fix: apply bot review suggestions (#3469)

Applied fixes from bot review comments:
- Comment #3587146944: Quote interpolated workflow_dir path in example

Assisted-By: 🤖 Claude Code

docs/reference/workflows.md

@@ -305,6 +305,8 @@ Steps can reference inputs and previous step outputs using `{{ expression }}` sy
 | `inputs.spec`                  | Workflow input values                |
 | `steps.specify.output.file`    | Output from a previous step          |
 | `item`                         | Current item in a fan-out iteration  |
+| `context.run_id`               | Current workflow run ID              |
+| `context.workflow_dir`         | Resolved absolute path to the workflow source directory. Empty string for string-loaded workflows. |
 
 Available filters: `default`, `join`, `contains`, `map`, `from_json`.
 
@@ -316,6 +318,14 @@ args: "{{ inputs.spec }}"
 message: "{{ status | default('pending') }}"
 ```
 
+## Shell Step Environment Variables
+
+Shell steps automatically receive the following environment variables:
+
+| Variable | Description |
+| -------- | ----------- |
+| `SPECKIT_WORKFLOW_DIR` | Resolved absolute path to the workflow source directory (same value as `{{ context.workflow_dir }}`). Not set when the workflow has no source path. |
+
 ## Input Types
 
 | Type      | Coercion                                          |