feat: add docfill mvp cli

docs/superpowers/specs/2026-06-18-docfill-mvp-design.md

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+# Docfill MVP Design
+
+## Goal
+
+Build the smallest local Go command-line tool that a digital employee can call to fill Word or Excel templates from Excel or SQLite data.
+
+## MVP Scope
+
+- Input data: `.xlsx` table or SQLite query result.
+- Template files: `.docx` or `.xlsx`.
+- Placeholder syntax: `{{column_name}}`.
+- Output: one generated file per input row.
+- Invocation: `docfill run --config task.json`.
+
+## Explicit Non-Goals
+
+- No web UI.
+- No permission system.
+- No workflow engine.
+- No template designer.
+- No direct business-system integration.
+- No AI guessing of fields.
+- No complex Word layout manipulation.
+
+## Config Shape
+
+```json
+{
+  "data": {
+    "type": "excel",
+    "path": "./data.xlsx",
+    "sheet": "Sheet1"
+  },
+  "template": {
+    "path": "./template.docx"
+  },
+  "output": {
+    "path": "./out/report_{{name}}_{{_row}}.docx"
+  }
+}
+```
+
+For SQLite, `data` uses `type: "sqlite"` and `query`.
+
+## Constraints
+
+- Keep the implementation boring and inspectable.
+- Infer template behavior from file extension.
+- Treat Excel first row or SQL column names as placeholder keys.
+- If a Word placeholder is split across Word XML runs, MVP may not replace it; users should type placeholders as plain contiguous text.

docs/superpowers/specs/2026-06-18-docfill-p0-cli-design.md

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+# Docfill P0 CLI Design
+
+## Goal
+
+Make the MVP safe enough for a digital employee to call repeatedly from scripts.
+
+## CLI Contract
+
+```bash
+docfill run --config task.json --var date=2026-06-18
+docfill run -c task.json --var date=2026-06-18 --var department=营销部
+```
+
+Exit codes:
+
+- `0`: success.
+- `1`: task execution or validation failed.
+- `2`: CLI usage error.
+
+Output:
+
+- Success writes a short generated-file summary to stdout.
+- Errors write one clear line to stderr with the `docfill:` prefix.
+
+Reserved for later:
+
+- `docfill validate`.
+- `--json`.
+
+## P0 Behavior
+
+- Resolve relative paths in config from the config file directory.
+- Support config vars and repeated CLI vars.
+- CLI vars override config vars.
+- Per-row data overrides vars during template rendering.
+- Generated `_row` is always the 1-based row number.
+- Support SQLite `params` for `?` query placeholders.
+- Support Excel `header_row`, 1-based, default `1`.
+- Do not overwrite existing output files unless `output.overwrite` is `true`.
+- Sanitize placeholder values only when rendering output file paths.
+- Fail if any template placeholder is missing from the current row context.
+- Fail if any `{{field}}` remains after rendering.
+
+## Config Shape
+
+```json
+{
+  "vars": {
+    "date": "2026-06-18"
+  },
+  "data": {
+    "type": "sqlite",
+    "path": "./data.db",
+    "query": "select name, done from daily where date = ?",
+    "params": ["{{date}}"]
+  },
+  "template": {
+    "path": "./template.docx"
+  },
+  "output": {
+    "path": "./out/report_{{date}}_{{name}}_{{_row}}.docx",
+    "overwrite": false
+  }
+}
+```