docs(reference): phase before project; flexible corp placeholder; type matrix

- Phase field listed before project in the tracking-number field order;
  example phase codes updated to ECI/EPC.
- Corporate placeholder rule clarified: 000000 is not mandatory — any
  easily recognizable, non-confusable value (e.g., CORP, HQ) works.
- Type codes shown as a discipline×type matrix for at-a-glance
  applicability instead of a stacked rowspan list.

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

reference.html

@@ -176,8 +176,8 @@ status       = "IFA" / "IFB" / "IFC" / "IFD" / "IFI" / "IFP" / "IFR" / "IFU" / "
         <p>Tracking numbers are composed of the following fields, in order:</p>
         <ul style="margin: var(--spacing-md) 0; padding-left: 1.5rem; color: var(--color-text-muted); line-height: 1.65;">
           <li><strong>originator</strong> — Organizational unit responsible for the deliverable</li>
-          <li><strong>project</strong> — Project identifier; 000000 reserved for corporate-scope deliverables</li>
+          <li><strong>[phase]</strong> — Optional phase code (e.g., <code>ECI</code>, <code>EPC</code>)</li>
-          <li><strong>[phase]</strong> — Optional phase code (e.g., P1, P2)</li>
+          <li><strong>project</strong> — Project identifier; a recognizable placeholder is used for corporate-scope deliverables</li>
           <li><strong>[area]</strong> — Optional area/budget code</li>
           <li><strong>discipline</strong> — Engineering or functional group (e.g., EL, ME, CV, PM)</li>
           <li><strong>type</strong> — Document category within discipline</li>
@@ -210,7 +210,7 @@ status       = "IFA" / "IFB" / "IFC" / "IFD" / "IFI" / "IFP" / "IFR" / "IFU" / "
             <tr>
               <td>With Phases</td>
               <td><code>originator-phase-project-discipline-type-sequence</code></td>
-              <td><code>ACME-P1-123456-EL-SPC-2623</code></td>
+              <td><code>ACME-ECI-123456-EL-SPC-2623</code></td>
             </tr>
             <tr>
               <td>Corporate</td>
@@ -221,7 +221,7 @@ status       = "IFA" / "IFB" / "IFC" / "IFD" / "IFI" / "IFP" / "IFR" / "IFU" / "
         </table>
 
         <div class="highlight-box" style="margin-top: var(--spacing-lg);">
-          <p><strong>Rule: 000000 placeholder.</strong> The Corporate schema uses <code>000000</code> as a reserved project placeholder, indicating the document belongs to the originator's corporate library rather than a specific project. The same originator code and discipline/type conventions apply, so corporate documents sort naturally alongside project documents in a unified archive.</p>
+          <p><strong>Rule: corporate placeholder.</strong> The Corporate schema substitutes a placeholder for the project identifier, indicating the document belongs to the originator's corporate library rather than a specific project. The placeholder does not have to be <code>000000</code> — any value works as long as it is <em>easily recognizable</em> as a corporate-scope marker and could not be mistaken for a real project number (e.g., <code>000000</code>, <code>CORP</code>, <code>HQ</code>). Pick one and use it consistently. The same originator code and discipline/type conventions apply, so corporate documents sort naturally alongside project documents in a unified archive.</p>
         </div>
 
         <h3>Discipline codes</h3>
@@ -268,38 +268,48 @@ status       = "IFA" / "IFB" / "IFC" / "IFD" / "IFI" / "IFP" / "IFR" / "IFU" / "
         <table>
           <thead>
             <tr>
-              <th scope="col">Discipline</th>
               <th scope="col">Type</th>
               <th scope="col">Description</th>
+              <th scope="col" class="text-center"><code>EL</code></th>
+              <th scope="col" class="text-center"><code>ME</code></th>
+              <th scope="col" class="text-center"><code>PM</code></th>
             </tr>
           </thead>
           <tbody>
             <tr>
-              <td rowspan="3"><code>EL</code></td>
               <td><code>SPC</code></td>
               <td>Specification</td>
+              <td class="text-center">✓</td>
+              <td class="text-center">✓</td>
+              <td class="text-center"></td>
             </tr>
             <tr>
               <td><code>DWG</code></td>
               <td>Drawing</td>
+              <td class="text-center">✓</td>
+              <td class="text-center"></td>
+              <td class="text-center"></td>
             </tr>
             <tr>
               <td><code>RPT</code></td>
               <td>Report</td>
-            </tr>
+              <td class="text-center">✓</td>
-            <tr>
+              <td class="text-center"></td>
-              <td rowspan="2"><code>ME</code></td>
+              <td class="text-center"></td>
-              <td><code>SPC</code></td>
-              <td>Specification</td>
             </tr>
             <tr>
               <td><code>MEMO</code></td>
               <td>Memorandum</td>
+              <td class="text-center"></td>
+              <td class="text-center">✓</td>
+              <td class="text-center"></td>
             </tr>
             <tr>
-              <td><code>PM</code></td>
               <td><code>MOM</code></td>
               <td>Minutes of Meeting</td>
+              <td class="text-center"></td>
+              <td class="text-center"></td>
+              <td class="text-center">✓</td>
             </tr>
           </tbody>
         </table>