Decomposes complex links into semantic header arguments with validation:

    #+HEADER: :transclude-type my-type
    #+HEADER: :my-component value
    #+begin_src elisp
    #+end_src

Direct links work without registration, including keywords:

    #+HEADER: :transclude [[file:/path::search]]
    #+HEADER: :transclude-keywords ":lines 10-15 :only-contents"
    #+begin_quote
    #+end_quote

Generic transclusion control headers work with all link types:

    #+HEADER: :transclude [[file:/path/file.txt]]
    #+HEADER: :transclude-lines 10-20

    #+HEADER: :transclude-type orgit-file
    #+HEADER: :orgit-repo ~/project
    #+HEADER: :orgit-file src/core.el
    #+HEADER: :transclude-thing defun

Generic headers (:transclude-lines, :transclude-thing) are mutually
exclusive and take precedence over :transclude-keywords specifications.

Variable substitution in headers:

Transclusion headers support variable references via :var:

    #+HEADER: :var repo="~/project"
    #+HEADER: :transclude-type orgit-file
    #+HEADER: :orgit-repo $repo
    #+HEADER: :orgit-file "src/core.el"

Two reference patterns are supported:
- $varname - Explicit dollar-prefixed reference
- varname - Bare name (when value is exactly the variable name)

Generic headers always support expansion:
- :transclude, :transclude-keywords, :transclude-lines, etc.

Type-specific headers opt in via :expand-vars property:
- See `org-transclusion-blocks-register-type' documentation
- Use `org-transclusion-blocks-describe-type' to check support

Babel control headers (:results, :session, etc.) are NEVER expanded
to avoid interfering with language backend variable handling.

Org syntax escaping prevents markup collisions:

Enabled by default for Org sources via
`org-transclusion-blocks-escape-org-sources'.  Override per-block with
:transclude-escape-org header or set file/subtree defaults via
#+PROPERTY: header-args.

Converting existing transclusions:

Existing #+transclude: keywords can be converted to header form:

    M-x org-transclusion-blocks-convert-keyword-at-point

Converts the keyword at point to equivalent header syntax. The
original line is preserved as a comment for reference.

For batch conversion:

    M-x org-transclusion-blocks-convert-keywords-in-buffer

Validator composition utilities:

- `org-transclusion-blocks-make-non-empty-validator'
- `org-transclusion-blocks-make-regexp-validator'
- `org-transclusion-blocks-make-predicate-validator'
- `org-transclusion-blocks-compose-validators'

See `org-transclusion-blocks-register-type' for type registration.

Commands:
- `org-transclusion-blocks-add' - Process block at point
- `org-transclusion-blocks-add-all' - Process all blocks in scope
- `org-transclusion-blocks-validate-current-block' - Test validators
- `org-transclusion-blocks-describe-type' - Show type documentation
- `org-transclusion-blocks-list-types' - List registered types