feat: place caller-provided files into the sandbox workspace (extra_files, --workspace-file) (#1085)

* add extra-files plumbing so orchestrators can drop single files into the sandbox workspace

* reject extra-file paths that collide with a local source tree

* add --workspace-file so CLI users can place files in the sandbox workspace

* reject repeated and control-character workspace paths

* revalidate persisted workspace files when resuming a run

* drop the workspace-file size limit

docs/usage/cli.mdx

@@ -37,6 +37,13 @@ strix (--target <target> | --target-list <path>) [options]
   Path to a file containing detailed instructions.
 </ParamField>
 
+<ParamField path="--workspace-file" type="string">
+  Path to a file on your machine to place into the sandbox workspace before the
+  scan starts. Repeat the option for more files. Write `PATH:DEST` to choose the
+  destination inside `/workspace`. `DEST` defaults to the file name. See
+  [Workspace files](/usage/instructions#workspace-files).
+</ParamField>
+
 <ParamField path="--scan-mode, -m" type="string" default="deep">
   Scan depth: `quick`, `standard`, or `deep`.
 </ParamField>
@@ -142,6 +149,10 @@ strix -t "postman://<collection-uuid>?env=<environment-uuid>"
 
 # Targets from a file
 strix --target-list ./targets.txt
+
+# Extra files placed in the sandbox workspace
+strix --target ./my-project --workspace-file ./wordlist.txt
+strix --target https://app.com --workspace-file ./openapi.yaml:specs/openapi.yaml
 ```
 
 ## Exit Codes

docs/usage/instructions.mdx

@@ -71,3 +71,43 @@ strix --target https://api.example.com \
 <Tip>
 Be specific. Good instructions help Strix prioritize the most valuable attack paths.
 </Tip>
+
+## Workspace files
+
+Instructions become part of the prompt. To give Strix a file to work with, such
+as a wordlist, an API specification, or notes, use `--workspace-file`. Strix
+places the file into the sandbox workspace before the scan starts.
+
+```bash
+strix --target https://app.com --workspace-file ./wordlist.txt
+```
+
+The file lands at `/workspace/<file name>`. To choose the destination, write
+`PATH:DEST`. `DEST` is a path inside `/workspace`.
+
+```bash
+strix --target https://app.com \
+  --workspace-file ./openapi.yaml:specs/openapi.yaml \
+  --workspace-file ./notes.md
+```
+
+Repeat the option for every file you want to place. Strix lists the files in the
+agent task, so the agent knows where to read them.
+
+Rules that apply to every workspace file:
+
+- The file is read-only inside the sandbox.
+- The destination must stay inside `/workspace`.
+- The destination must not fall inside a target directory, because target files
+  come from the target itself. Strix skips such a file and logs a warning.
+- Two files cannot claim the same destination.
+
+<Note>
+A workspace file is data for the agent to use. It is not a scan target, and its
+contents do not change the instructions.
+</Note>
+
+<Warning>
+Do not place secrets in a workspace file. The sandbox runs untrusted target
+code, so treat anything you place there as readable by the target.
+</Warning>