TASK-006/007/015: housekeeping — normalize status to Done

All three are functionally complete in code and merged on the integration
branch. This commit only updates the status field to the canonical "Done"
value to keep tooling that reads the spec consistent.

- TASK-006: status was "Complete" (non-canonical phrasing). #define
  value-constants migrated to httpserver::constants; index row already
  said Done.
- TASK-007: status carried a forward-reference to TASK-020. With
  TASK-020 merged, the hygiene gate is in full-enforcement mode
  (HEADER_HYGIENE_STRICT ?= yes, XFAIL_TESTS line removed, public hpps
  free of backend includes). Index row already said Done.
- TASK-015: status was "In Progress" though all action items were
  checked. http_request PIMPL pointer is in place, detail/
  http_request_impl.hpp exists, and http_request.hpp no longer pulls
  <microhttpd.h>/<gnutls/gnutls.h>. Index row also synced.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: etr

specs/tasks/M1-foundation/TASK-006.md

@@ -27,4 +27,4 @@ Eliminate macro pollution from public headers by moving every `#define` constant
 **Related Requirements:** PRD-CFG-REQ-002
 **Related Decisions:** §4.9
 
-**Status:** Complete
+**Status:** Done

specs/tasks/M1-foundation/TASK-007.md

@@ -26,7 +26,7 @@ Lock in the "no backend headers leak through `<httpserver.hpp>`" invariant with
 **Related Requirements:** PRD-HDR-REQ-001..003
 **Related Decisions:** §9 testing item 1
 
-**Status:** Done (informational gate landed; full enforcement at TASK-020)
+**Status:** Done
 
 ---
 

specs/tasks/M3-request/TASK-015.md

@@ -28,4 +28,4 @@ Move `http_request`'s backend-coupled members (`MHD_Connection*`, raw GnuTLS han
 **Related Requirements:** PRD-HDR-REQ-001..004
 **Related Decisions:** DR-003b, §4.2
 
-**Status:** In Progress
+**Status:** Done

specs/tasks/_index.md

@@ -97,7 +97,7 @@ Nominally: **13 sequential tasks**, each S–XL. Most other tasks parallelize of
 | TASK-012 | `http_response` fluent `with_*` setters | M2 | Done | TASK-009 |
 | TASK-013 | Remove `*_response` subclasses and dispatch virtuals | M2 | Done | TASK-009, TASK-010, TASK-011, TASK-012 |
 | TASK-014 | `webserver_impl` skeleton (PIMPL prep) | M3 | Done | TASK-002 |
-| TASK-015 | `http_request_impl` skeleton (PIMPL split) | M3 | In Progress | TASK-002, TASK-014 |
+| TASK-015 | `http_request_impl` skeleton (PIMPL split) | M3 | Done | TASK-002, TASK-014 |
 | TASK-016 | Per-connection arena for `http_request_impl` | M3 | Done | TASK-014, TASK-015 |
 | TASK-017 | `http_request` container getters return `const&` | M3 | Done | TASK-015 |
 | TASK-018 | `http_request` single-key getters return `string_view`, all const | M3 | Done | TASK-015, TASK-016 |